



% 



? 



" » ■■• A >7- * * \ .in, v^. ,A 






\ 






"'/ 







-1 z 



.0 < 










I 




* 





ELEMENTARY ZOOLOGY 



BY 



VERNON L. KELLOGG, M.S. 

Professor of Entomology, Leland Stan/ord Junior University 



SECOND EDITION, REVISED 




-» « V 



3 9 S 



NEW YORK 

HENRY HOLT AND COMPANY 
1902 



THE LIBRARY OF 
CONGRESS, 

Two Copies Received 

JUN. 11 1902 

Copyright entry 

3LASS &- XXc. No 

COPY B. 



Copyright, 1901, 

BY 

HENRY HOLT & CO. 



' i c « l ( c C 

CC €;«« c C « 

c* e * t c « e c c 



o etc 

( t 

c c c c c • 









Q.L41 
.'K3 



ROBERT DRUMMOND, PRINTER, NEW YORK 



PREFACE 

It seems to the author that three kinds of work should 
be included in the elementary study of zoology. These 
three kinds are: (a) observations in the field covering 
the habits and behavior of animals and their relations 
to their physical surroundings, to plants, and to each 
other ; (b) work in the laboratory, consisting of the study 
of animal structure by dissection and the observation of 
live specimens in cages and aquaria ; and (V) work in the 
recitation- or lecture-room, where the significance and 
general application of the observed facts are considered 
and some of the elementary facts relating to the classifi- 
cation and distribution of animals are learned. 

These three kinds of work are represented in the course 
of study outlined in this book. The sequence and extent 
of the study in laboratory and recitation-room are defi- 
nitely set forth, but the references to field-work consist 
chiefly of suggestions to teacher and student regarding 
the character of the work and the opportunities for it. 
Not because the author would give to the field-work the 
least important place, — he would not, — but because of the 
utter impracticability of attempting to direct the field- 
work of students scattered widely over the United States. 
The differences in season and natural conditions in vari- 
ous parts of the country with the corresponding differences 
in the " seasons " and course of the life-history of the 

iii 



iv PREFACE 

animals of the various regions make it impossible to in- 
clude in a book intended for general use specific direc- 
tions for field-work. Further, the amount of time for 
field-work at the disposal of teacher and class and the 
opportunities afforded by the topographic character of the 
region in which the schools are located vary much. The 
initiation and direction of this must therefore always de- 
pend on the teacher. On the other hand, the work of the 
other two phases of study can to a large extent be made 
pretty uniform throughout the country. For dissection, 
specimens properly killed and preserved are about as 
good as fresh material, and by modifying the suggested 
sequence of work a little to suit special conditions or con- 
veniences, the examination of live specimens in the 
laboratory can in most cases be accomplished. 

The author believes that elementary zoological study 
should not be limited to the examination of the struc- 
ture of several types. The student should learn by 
observation something of the functions of animals and 
something of their life-history and habits, and should be 
given a glimpse of the significance of his particular ob- 
servations and of their general relation to animal life as a 
whole. The drill of the laboratory is perhaps the most 
valuable part of the work, but as a matter of fact the high 
school is trying to teach elementary zoology, an ele- 
mentary knowledge of animals and their life, and dissec- 
tion alone cannot give the pupil this knowledge. On the 
other hand, without a personal acquaintance with animals, 
based on careful actual observations of their life-history 
and habits and on the study of the structural characters of 
the animal body by personally made dissections, the 
pupil can never really appreciate and understand the life 
of animals. Reading and recitation alone can never 
give the student any real knowledge of it. 

The book is divided into three parts, of which Part I 



PREFACE V 

should be * first undertaken. This is an introduction to 
an elementary knowledge of animal structure, function, 
and development. It consists of practical exercises in 
the laboratory, each followed by a recitation in w 7 hich the 
significance of the facts already observed is pointed out. 
The general principles of zoology are thus defined on a 
basis of observed facts. 

Part II is devoted to a consideration of the principal 
branches of the animal kingdom ; it deals with t system- 
atic zoology. In each branch one or more examples 
are chosen to serve as types. The most important struc- 
tural features of these examples are studied, by dissection, 
in the laboratory. The directions for these dissections 
consist of technical instructions for dissecting, the calling 
attention to and naming of principal parts, together with 
questions and demands intended to call for independent 
work on the part of the .student. The directions follow 
the actual course of the dissection instead of being ar- 
ranged according to systems of organs, and are intended 
for the orientation of the student and not to be in them- 
selves expositions of the anatomy of the types. The 
condensation of these directions is made more feasible by 
the presence of anatomical plates (drawn directly from 
dissections). Following the account of the dissection of 
the type are brief notes on its life-history and habits. 

* This is true if a strictly logical treatment of the subject is held to. As 
a matter of fact, it is often of advantage to begin with, or at least to take up 
from the beginning in connection with the indoor work, some field-work, 
such as the collecting and classifying of insects and the observation of 
their metamorphosis. As most schools begin work in the fall, advantage 
must be taken of the favorable opportunities for field-work at the beginning 
of the year. These opportunities are of course much less favorable in the 
winter. 

f The classification of animals used in this book is that adopted in 
Parker and Haswell's " Text-book of Zoology" (2 vols., 1897, Macmillan 
Co.). Exception is made in the case of the worms, which are considered 
as a single branch, Vermes, instead of as several distinct branches. 



vi PREFACE 

Then follows a general account of the branch to which 
the example dissected belongs and brief accounts of 
some of the more interesting members of the branch. In 
these accounts technical directions are given for brief 
comparative examinations and for the study of the life- 
history and habits of some of the more accessible of 
these forms. 

It will not be possible, of course, to undertake with any 
thoroughness the consideration of all of the branches of 
animals in a single year. But all are treated in the book, 
so that the choice of those to be studied may rest with the 
teacher. This choice will of necessity depend largely on 
the opportunities afforded by the situation of the school, 
as, for example, whether on the seashore or in the interior 
near a lake or river, or on the dry plains, and on the re- 
lation of the school-terms to the seasons of the year. 
The branches are arranged in the book so that the sim- 
plest animals are first considered, the slightly complex 
ones next, and lastly the most highly organized forms. 
But if in order to obtain examples for study it is necessary 
to take up branches irregularly, that need not prove con- 
fusing. The author would suggest that whatever other 
branches are studied, the insects and birds, which are 
readily available in all parts of the country, be certainly 
selected, and with this selection in view has given them 
special attention. Indeed some teachers may find these 
two branches to offer quite sufficient work in classificatory 
and ecological lines. 

Part III is devoted to a necessarily brief consideration 
of certain of the more conspicuous and interesting 
features of animal ecology. It has in it the suggestion 
for much interesting field-work. The work of this part 
should be taken up in connection with that of Part II, as, 
for example, the consideration of social and communal 
life in connection with the insects, parasitism in connec- 



PREFACE vii 

tion with the worms, and also with the insects, distribu- 
tion in connection with the birds, perhaps, and so on. 

In appendices there are added some suggestions for 
the outfitting of the laboratory, and a list of the equip- 
ment each student should have. Here, also, is appended 
a list of a few good authoritative reference books which 
should be accessible to students and to which specific 
references are made in the course of this book. Some 
practical directions for the collecting and preserving of 
specimens are also given. (Suggestions for the obtaining 
of material for the various laboratory exercises outlined 
in the book are to be found in " technical notes " in- 
cluded in the directions for each exercise.) The author 
believes that the building up of a single school-collection 
in which all the pupils have a common interest and to 
which all contribute is to be encouraged rather than the 
making of separate collections by the pupils. Waste of 
life is checked by this, and in time, with the contributions 
of succeeding classes, a really good and effective collec- 
tion may be built up. The "collecting interest" can 
be taken advantage of just as well in connection with a 
school-collection as with individual collections. 

The plates illustrating the dissections have all been 
drawn originally for the book from actual dissections. 
Most of the other figures are original, either drawn or 
photographed directly from nature, or from preserved 
specimens. Credit is given in each case for figures not 
original. The drawings for all of the figures of dis- 
sections and for all original figures not otherwise accred- 
ited were made by Miss Mary H. Wellman, to whom the 
author expresses his obligations. The thanks of the 
author are due to Mr. George Otis Mitchell, San Fran- 
cisco, who kindly made the photo-micrographs of insect 
structure from the author's slides; to Professor Mark V. 
Slingerland, Cornell University, for electros of his photo- 



vin PREFACE 

graphs of insects; to Dr. L. 0. Howard, U. S. Entomol- 
ogist, for electros of figs. 45, 52, 56, 68, 81, 82, 83, 
84, 87, 90, and 92; to Professor L. L. Dyche, University 
of Kansas, for photographs of his mounted groups of 
mammals; to Mrs. Elizabeth Grinnell, Pasadena, Calif., 
for photographs of birds; to Mr. J. O. Snyder, Stanford 
University, for photographs of snakes; to Mr. Frank 
Chapman, editor of " Bird-lore," for electros of photo- 
graphs of birds; to Mr. G. O. Shields, editor of " Recrea- 
tion," for an electro of the photograph of a bird; to the 
American Society of Civil Engineers for electros of photo- 
graphs of boring marine worms; to Cassell & Co., for 
electros of three photographs from nature; to Geo. A. 
Clark, secretary Fur Seal Commission for photographs of 
seals; and to the Whitaker and Ray Co., San Francisco, 
for electros of figs. 46, 59, 60, 61, 64, 65, 93, 94, 97, 98, 
99, 100, 102, 119, and 166 to 172, published originally in 
Jenkins & Kellogg's ''Lessons in Nature Study.' The 
origin of each of these pictures is specifically indicated in 
connection with its use in the book. 

The author's sincere thanks are also due to Mrs. David 
Starr Jordan and to Mr. J. C. Brown, graduate student in 
zoology in Stanford University, for their assistance in the 
correction of the MS., and in the preparation of the lab- 
oratory exercises respectively. The chapters of Part II 
relating to the vertebrates were read in MS. by President 
David Starr Jordan, whose aid and courtesy are gratefully 
acknowledged. Similar acknowledgments are due Pro- 
fessors Harold Heath and R. E. Snodgrass for read- 
ing the proofs of the directions for the laboratory ex- 
ercises. 

Vernon Lyman Kellogg. 

Stanford University, May, 1901. 



CONTENTS 



PART I 

STRUCTURE, FUNCTIONS, AND DEVELOPMENT OF 

ANIMALS 

I. -THE STUDY OF ANIMALS AND THEIR LIFE. 

Our familiar knowledge of animals and their life, I. — Zoology and its 
divisions, 2. — A first course in Zoology, 3. 

II.— THE GARDEN TOAD (Bufo Lentiginosis). 

[Laboratory exercise], 5. — External structure, 5. — Internal structure, 7. 

III.— THE STRUCTURE AND FUNCTIONS OF THE ANIMAL BODY. 

Organs and functions, 14. — The animal body a machine, 14. — The essen- 
tial functions or life-processes, 15. 

IV.— THE CRAYFISH (Cambarus sp.). 
[Laboratory exercise], 17. — External structure, 17. — Internal structure, 21. 

V.— THE MODIFICATION OF ORGANS AND FUNCTIONS. 

Difference between crayfish and toad, 26. — Re-emblances between cray- 
fish and toad, 27. — Modification of functions and structure to fit the animal 
to the special conditions of its life, 29. — Vertebrate and invertebrate, 30. 

VI.— AMCEBA AND PARAMECIUM. 

[Laboratory exercise], 31. — Amoeba, 31. — The slipper-animalcule (Para- 
mecium sp.), 34. 

ix 



* CONTENTS 

VII.— THE SINGLE -CELLED ANIMAL BODY; PROTOPLASM 

AND THE CELL. 

The single-celled animal body, 36. — The cell, 37. — Protoplasm, 39. 

VIII. -CELLULAR STRUCTURE OF THE TOAD (OR FROG). 

[Laboratory exercise], 40. — The blood, 40. — The skin, 40. — The liver. 
41. — The muscles, 41. 

IX.— THE MANY-CELLED ANIMAL BODY; DIFFERENTIATION 

OF THE CELL. 
The many-celled animal body, 43. — Differentiation of the cell, 43. 

X.— HYDRA. 

[Laboratory exercise], 46. 

XL— THE SIMPLEST MANY-CELLED ANIMALS. 

Cell-differentiation and body-organization in Hydra, 52. — Degrees in 
cell-differentiation and body-organization, 54. 

XII.— DEVELOPMENT OF THE TOAD. 
[Field and laboratory exercise], 55. 

XIIL— MULTIPLICATION AND DEVELOPMENT. 

Multiplication, 57. — Spontaneous generation, 58. — Simplest multiplica- 
tion and development, 59.— Birth and hatching, 61. — Life-history, 62. 



PART II 

SYSTEMATIC ZOOLOGY 

XIV.— THE CLASSIFICATION OF ANIMALS. 
[Laboratory exercise and recitation], 65. — Basis and significance 01 
classification, 65. — Importance of development in determining classification, 
67. — Scientific names, 68. — An example of classification, 68. — Species, 
69. -Genus, 70. — Family, 72. — Order, 72. — Class and branch, 73. 

XV.— BRANCH PROTOZOA : THE ONE-CELLED ANIMALS. 
Example : The bell animalcule (Vorticella sp.) [Laboratory 
exercise], 75. 

Other Protozoa. 

Form of body, 78. — Marine Protozoa, 80, 



CONTENTS xi 

XVI.— BRANCH PORIFERA: THE SPONGES. 

Example: The Fresh-water sponge (Spongilla sp.) [Laboratory 
exercise], 84. 

Example: A calcareous ocean-sponge (Grantia sp.) [Laboratory 
exercise], 85. 

Example: A commercial sponge [Laboratory exercise], 86. 

Other Sponges. 

Form and size, 87. — Skeleton, 88. — Structure of body, 88. — Feeding 
habits, 88. — Development and life-history, 89. — The sponges of commerce, 
90. — Classification, 91. 

XVII.— BRANCH CCELENTERATA: THE POLYPS, SEA- 
ANEMONES, CORALS, AND JELLYFISHES. 

Polyps, sea-anemones, corals, and jellyfishes. 

General form and organization of body, 93. — Structure, 94. — Skeleton, 
95. — Development and life-history, 95. — Classification, 96.— The polyps, 
colonial jellyfishes, etc. (Hydrozoa), 97. — The large jellyfishes, etc. 
(Scyphozoa), 1 01. — The sea-anemones and corals (Actinozoa), 102. — The 
Ctenophora, 107. 

XVIIL— BRANCH ECHINODERMATA : THE STARFISHES, SEA- 
URCHINS, SEA CITUMBERS, ETC. 

Example : Starfish (Asterias sp.) [Laboratory exercise]. — External 
structure, 108. — Internal structure, 110. — Life-history and habits, 113. 

Example : Sea-urchin (Strongylocentrus sp.) [Laboratory exercise]. 
■ — External structure, 113. 

Other Starfishes, Sea-urchins, Sea-cucumbers, etc. 

Shape and organization of body, 116. — Structure and organs, 117. — De- 
velopment and life-history, 119. — Classification, 120. — Starfishes (Asteroi- 
dea), 121. — Brittle stars (Ophiuroidea), 122. — Sea-urchins (Echinoidea), 
123. — Sea-cucumbers (Holothuroidea), 124. — Feather-stars (Crinoidea), 125. 

XIX.— BRANCH VERMES: THE WORMS. 

Example: The Earthworm Lumbricus sp.) [Laboratory exercise]. 

External structure, 127. — Internal structure, 129. — Life-history and habits, 

133- 
Other Worms. 

Classification, 135. — Earthworms and leeches (Oligochaeh-e . 136. — Flat 
worms (Platyhelminthes). 137. — Round worms (Nemathelminthes), 140. — 
Wheel-animalcules (Rotifera), 142. 



xii CONTENTS 

XX.— BRANCH ARTHROPODA : THE CRUSTACEANS, CEN- 
TIPEDS, INSECTS, AND SPIDERS. 

Class Crustacea: Crayfishes, crabs, lobsters, etc. 

Example; The crayfish (Cambarus sp.). Structure, 146. — Life-his- 
tory and habits, 146. 

Other Crustaceans. 

Body form and structure, 147. — Water-fleas (Cyclops), 148. — Wood-lice 
(Isopoda), 150. — Lobsters, shrimps, and crabs (Decapoda), 151. — Barnacles, 

i55- 

XXL— BRANCH ARTHROPODA (CONTINUED). 

Class Insecta : The Insects. 

Example : The red-legged locust (Melanoplus femur-rubrum), 
[Laboratory exereise]. External structure, 157. —Life-history and habits, 
161. 

Example: The water- scavenger beetle (Hyerophilus sp.) [Labo- 
ratory exercise]. External structure, 163. — Internal structure, 166. — Life- 
history and habits, 169. 

Example : The monarch butterfly (Anosia plexippus) [Laboratory 
exercise]. External structure, 171. — Life-history and habits, 175. 

Example : Larva of monarch butterfly [Laboratory exercise] . 
Structure, 177. 

Other Insects. 

Body form and structure. 181. — Development and life-history, 188. — - 
Classification, 191. — Locusts, cockroaches, crickets, etc. (Orthoptera), 192. 
— The dragon-flies and May-flies (Odonata and Ephemerida), 194. — The 
sucking-bugs (Hemiptera), 197. — The flies (Diptera), 201. — The butterflies 
and moths (Lepidoptera), 205. — The beetles (Coleoptera), 206. — The 
ichneumon flies, ants, wasps, and bees (Hymenoptera), 212. 

Class Myriapoda : The centipeds and millipeds. 

Class Arachnida : The scorpions, spiders, mites, and tics. 

XXII.— BRANCH MOLLUSCA : THE MOLLUSCS. 

Example : The fresh-water mussel (Unio sp.) [Laboratory exercise]. 
Structure, 239. — Life-history and habits, 243. 

Other Molluscs. 

Body form and structure, 245. — Development, 246. — Classification, 246. 
— Clams, scallops, and oysters (Pelecypoda), 246. — Snails, slugs, nudi- 
branchs, and " sea-shells " (Gastropoda), 252.— Squids, cuttlefishes, and 
octopi (Cephalopoda), 255. 



CONTENTS xin 

XXIII.— BRANCH CHORDATA: THE ASCIDIANS, VERTE- 
BRATES, ETC. 

Structure of the vertebrates, 259. — Classification of the Chordata, 260. — 
The ascidians, 261. 

XXIV.— BRANCH CHORDATA (CONTINUED). 

Class Pisces : The Fishes. 

Example : The golden sun fish Eupomotis gibbosus) [Laboratory 
exercise]. External structure, 263. — Internal structure. 265. — Life-history 
and habits, 270. 

Other Fishes. 

Body form and structure, 271. — Development and life-history, 276. — 
Classification, 277. — The lancelets (Leptocardii), 277. — The lampreys and 
hag fishes (Cyclostomata), 278. — The true fishes (Pisces), 279. — The sharks, 
skates, etc. (Elasmobranchiij. 279. — The bony fishes (Teleostomi), 281. — 
Habits and adaptations, 285. —Food-fishes and fish-hatcheries, 288. 

XXV.— BRANCH CHORDATA (CONTINUED). 

Class Batrachia : The Batrachians. 

Body form and organization. 292.— Structure, 293. — Life-history and 
habits, 295. — Classification, 297. — Mud-puppies, salamanders, etc. (Uro- 
dela), 297. — Frogs and toads (Anura), 299. — CceciHans (Gymnophiona), 
302. 

XXVI. —BRANCH CHORDATA (CONTINUED). 

Class Reptilia: The snakes, lizards, turtles, crocodiles, etc. 

Example : The garter snake (Thamnophis sp.) [Laboratory exer- 
cise]. Structure, 303. — Life -history and habits, 308. 

Other Reptiles. 

Body form and organization, 310. — Structure, 311, — Life-history and 
habits, 312. — Classification, 313. — Tortoises and turtles (Chelonia), 314. — 
Snakes and lizards (Squamata), 317. — Crocodiles and alligators ^Croco- 
dilia), 325. 

XXVII.— BRANCH CHORDATA (CONTINUED). 

Class Aves : The Birds. 

Example: The English Sparrow iPasser domesticus) [Laboratory 
exercise]. External structure. 327. — Internal structure [Laboratory exer- 
cise], 329. — Life history and habits, 335. 

Other Birds. 

Body form and structure, 336. — Development and life-history, 339. — 
Classification. 340. — The ostriches, cassowaries, etc. (Ratitae), 341. — The 



xiv CONTENTS 

loons, grebes, auks, etc. (Pygopodes), 343. — The gulls, terns, petrels, and 
albatrosses (Longipennes), 345. — The cormorants, pelicans, etc. (Stegano- 
podes), 346. — The ducks, geese, and swans (Anseres), 347. — The ibises, 
herons, and bitterns (Herodiones), 347. — The cranes, rails, and coots (Palu- 
dicolse), 348. — The snipes, sand-pipers, plovers, etc. (Limicolae), 349. — 
The grouse, quail, pheasants, turkeys, etc. (Gallinse), 358. — The doves and 
pigeons (Columbse), 351. — The eagles, hawks, owls, and vultures (Raptores), 
351. — The parrots (Psittaci), 353. — The cookoos and kingfishers (Coccyges), 
354. — The woodpeckers (Pici), 354.— The whippoorwills, chimney-swifts, 
and humming-birds (Macrochires), 356. — The perchers (Passeres), 357. — 
Determining and studying the birds of a locality, 359. — Bills and feet, 362. 
— Flight and songs, 364. — Nestling and care of the young, 366. — Local dis- 
tribution and migration, 367. — Feeding habits, economics, and protection of 
birds, 370. 

XXVIIL— BRANCH CHORDATA (CONTINUED). 

Class Mammalia : The Mammals. 

Example : The Mouse (Mus musculus) [Laboratory exercise]. Struc- 
ture, 373. — Life-history and habits, 379. 

Other Mammals. 

Body form and structure, 381. — Development and life-history, 387. — 
Habits, instincts, and reason, 387. — Classification, 388. — The opossums 
(Marsupialia), 389. — The rodents or gnawers (Glires), 390. — The shrews 
and moles (Insectivora), 391. — The bats (Chiroptera), 391. — The dolphins, 
porpoises, and whales (Cete), 393.— The hoofed mammals (Ungulata), 394. 
— The carnivores (Ferae), 396. — The man-like mammals (Primates), 398. 

PART III 

ANIMAL ECOLOGY 

XXIX.— THE STRUGGLE FOR EXISTENCE, ADAPTATION, 
AND SPECIES-FORMING. 

The multiplication and crowding of animals, 404. — The struggle for 
existence, 406. — Variation and natural selection, 406. — Adaptation and 
adjustment to surroundings, 407.— Species forming, 408. — Artificial selec- 
tion, 409. 

XXX.— SOCIAL AND COMMUNAL LIFE, COMMENSALISM, AND 

PARASITISM. 

Social life and gregariousness, 410.— Communal life, 411,— Commen- 
salism 413. — Parasitism, 415. 



CONTENTS xv 

XXXL— COLOR AND PROTECTIVE RESEMBLANCES. 

Use of color, 424. — General, variable, and special protective resemblance, 
426. — Warning colors, terrifying appearances, and mimicry, 430. — Alluring 
coloration, 433. 

XXXII. —THE DISTRIBUTION OF ANIMALS. 

Geographical distribution, 435. — Laws of distribution, 437. — Modes of 
migration and distribution, 437. — Barriers to distribution, 438. — Faunae 
and zoogeographic areas, 440. — Habitat and species, 441. — Species-extin- 
guishing and species-forming, 442. 



APPENDICES 

EQUIPMENT AND METHODS 

APPENDIX I.— EQUIPMENT AND NOTES OF PUPILS. 

Equipment of pupils, 447. — Laboratory drawings and notes, 447. — Field 
observations and notes, 448. 

APPENDIX II.— LABORATORY EQUIPMENT AND METHODS. 

Equipment of laboratory, 450. — Collecting and preparing material for use 
in the laboratory, 451. — Obtaining marine animals, microscopic prepara- 
tions, etc., 453. — Reference-books, 454. 

APPENDIX III.— REARING ANIMALS AND MAKING COLLEC- 
TIONS. 

Live cages and aquaria, 457. — Making collections. 461. — Collecting and 
preserving insects, 463. — Collecting and preserving birds, 466. — Collecting 
and preserving mammals, 470. — Collecting and preserving other animals, 
472. 



PART I 

STRUCTURE, FUNCTIONS, AND DEVELOP- 
MENT OF ANIMALS 

CHAPTER I 
THE STUDY OF ANIMALS AND THEIR LIFE 

Our familiar knowledge of animals and their life.— 

We are familiarly acquainted with dogs and cats ; less 
familiarly probably with toads and crayfishes, and we 
have little more than a bare knowledge of the existence 
of such animals as seals and starfishes and reindeer. But 
what real knowledge of dogs and toads does our familiar 
acquaintanceship with them give ? Certain habits of the 
dog are known to us: it eats, and eats certain kinds of 
food ; it runs about ; it responds to our calls or even to 
the mere sight of us ; it evidently feels pain when struck, 
and shows fear when threatened. Another class of 
attributes of the dog includes those things that we know 
of its bodily make-up: its possession of a head with eyes 
and ears, nose and mouth; its four legs with toes and 
claws; its covering of hair. We know, too, that it was 
born alive as a very small helpless puppy which lived for 
a while on food furnished by the mother, and that it has 
grown and developed from this young state to a fully 
grown, fully developed dog. We know also that our 
dog is a certain kind of dog, a spaniel, perhaps, while 



2 ELEMENTARY ZOOLOGY 

our neighbor's dog is of another kind, a greyhound, it 
may be. We know accordingly that there are different 
kinds of tame dogs, and we may know that wolves 
are so much like dogs that they might indeed be 
called wild dogs, or dogs called a kind of tame wolf. 
But how little we really know about the dog's body and 
its life is apparent at a moment's thought. We see only 
the outside of the dog, but w r hat an intricate complex of 
parts really composes this animal ! We see it eat and 
breathe and run ; of what is done with the food and air 
inside its body, and of the series of muscle contractions 
and mechanical processes which cause its running, we have 
but the slightest conception. We see that the pup gets 
larger, that is, grows; that it changes gradually in appear- 
ance, that is, develops; but of the real processes and 
changes that take place in growth and development how 
little we know ! We know that there are other kinds of 
dogs; that wolves and foxes are relatives of the dog; and 
we have heard that cats and tigers are relatives also, 
although more distant ones. We know, too, that all the 
backboned animals, some of them very unlike dogs, are 
believed to be related to each other, but of the thousands of 
these animals and of their relationships our knowledge is 
scanty. Finally, of the relations of the dog, and of other 
animals, to the outside world, and of the wonderful man- 
ner in which the dog's make-up and behavior fit it to live 
in its place in the world under the conditions that surround 
it, we have probably least knowledge of all. 

Zoology and its divisions. — What things we do know 
about the dog, however, and about its relatives, and 
what things others know, can be classified into several 
groups, namely, things or facts about what the dog does, 
or its behavior, things about the make-up of its body, 
things about its growth and development, things about 
the kind of dog it is and the kinds of relatives it has, and 



THE STUDY OF ANIMALS AND THEIR LIFE 3 

things about its relations to the outer world, and its special 
fitness for life. 

All that is known of these different kinds of facts about 
the dog constitutes our knowledge of the dog and its life. 
All that is known by scientific men and others of these 
different kinds of facts about all the 500,000 or more kinds 
of living animals, constitutes our knowledge of animals and 
is the science zoology * Names have been given to these 
different groups of facts about animals. The facts about 
the bodily make-up or structure of animals constitute that 
part of zoology called animal anatomy or morpliology; the 
facts about the things animals do, or the functions of 
animals, compose animal physiology; the facts about the 
development of animals from young to adult condition are 
the facts of animal development; the knowledge of the 
different kinds of animals and their relationships to each 
other is called systematic zoology or animal classification; 
and finally the knowledge of the relations of animals to 
their external surroundings, including the inorganic world, 
plants and other animals, is called animal ecology. 

Any study of animals and their life, that is, of zoology, 
may include all or any of these parts of zoology. Most 
zoologists do, indeed, devote their principal attention to 
some one group of facts about animals and are accordingly 
spoken of as anatomists, or physiologists, systematists, 
and so on. But such a specialization of study should be 
made only after the zoologist has acquired a knowledge 
of the principal or fundamental facts in all the other 
branches of zoology. 

A first course in zoology. — The first " course," then, 
in the study of animals should include the fundamental 
facts in all these branches or parts of zoology. That is 
what the course outlined in this book tries to cover. 

* Zoology is formed, from two Greek words: zoon, meaning animal, and 
logos, meaning discourse. 



4 ELEMENTARY ZOOLOGY 

But no text-book of zoology can really give the student 
the knowledge he seeks. He must find out most of it for 
himself; a text-book, based on the experiences of others, 
is chiefly valuable for telling him how to work most 
effectively to get this knowledge for himself. And the 
best students always find out things which are not in books. 
Especially can the beginning student find out things not 
known before, "new to science," as we say, about the 
behavior and habits of animals, and their relations to their 
surroundings. The life-history of comparatively few kinds 
of animals is exactly known; the instincts and habits of 
comparatively few have been studied in any detail. The 
kinds of food demanded, the feeding habits, nest-building, 
care of the young, cunning concealment of nest and self, 
time of egg-laying or of producing young, duration of the 
immature stages and the habits and behavior of the young 
animals — a host, indeed, of observations on the actual life 
of animals, remain to be made by the "field naturalist.' 
Any beginning student can be a "field naturalist" and 
can find out new things about animals, that is, can add 
to the science of zoology. 



CHAPTER II 
THE GARDEN TOAD {Bufp lentiginosus) 

LABORATORY EXERCISE 

Technical Note. — Although this description is written for the 
toad it will fit for the dissection of the frog. It will be found, after 
casting aside a few ungrounded prejudices, that the toad is the 
better for class dissection. Toads are best collected about dusk, 
when they can be picked up in almost any garden in town or in the 
country. During the spring many can be found in the ponds where 
they are breeding. To kill the toad place it in an air-tight vessel 
with a piece of cotton or cloth saturated in chloroform or ether. 
When the toad is dead, wash off the specimen and put in a dissect- 
ing pan for study. Several specimens should be placed in a nitric 
acid solution for a day or so (for directions for preparing, see 
p. 12) to be used later for the study of the nervous system. Also 
several specimens should be injected for the better study of the 
circulatory system. With an injecting mass made as directed on 
p. 451 introduce through a small canula into the ventricle of the 
heart. This will inject the arterial system, and with increased 
pressure the injecting mass may be forced through the valves of the 
heart, thus passing into the auricles and throughout the venous 
system. After injecting use the specimen fresh or after it has been 
preserved in 4% formalin. 

External structure. — Note that the body of the toad 
is divided into several principal regions or parts, as is the 
human body, namely, a head, upper limbs, trunk, and 
lower limbs. As you look at the toad note the similarity 
of the parts on one side to those of the other, as right leg 
corresponding to left leg, right eye to left eye, etc. This 
arrangement of the body in similar halves among animals 
is known as bilateral symmetry. As a rule animals which 
show bilateral symmetry move in a definite direction. 
The part that moves forward is the anterior end, while 

5 



6 ELEMENTARY ZOOLOGY 

the opposite extremity is the posterior end. In most 
animals we note two other views or aspects ; that which 
is called the "back' and with most animals is, under 
ordinary conditions, uppermost is the dorsum or dorsal 
aspect, while that which lies below is the venter or ventral 
aspect. When referring to a view from one side we speak 
of it as a right or left lateral aspect. These terms hold 
good for most of the animals that we shall study. 

Note at the anterior end of the toad a wide transverse 
slit, the mouth. What other openings are on the anterior 
end ? Note the two large eyes, the organs of sight. Just 
back of each eye note an elliptical, smooth membrane. 
This is the tympanum of the outer ear, and through this 
membrane the vibrations produced by sound-waves are 
transferred to the inner ear, which receives sensations and 
transmits them to the brain. Open the mouth by drawing 
down the lower jaw. Note just within the angle of the 
lower jaw the tongue. How is it attached to the wall of 
the mouth ? On the tongue are a great many fine papillce 
in which is located the sense of taste. It has now been 
seen that most of the special senses of the toad have their 
seat in the head. Pass a straw or bristle into one of the 
nostrils. Where does it come out ? These internal 
openings to the nose are the inner nares. Note in the 
roof of the mouth just posterior to each of the eyeballs an 
opening. These are the internal openings to the wide 
Eustachian tubes, which lead to the mouth from the 
chamber of the ear behind the tympanum. 

Note far back in the mouth an opening through which 
food passes. This is the oesophagus or gullet. Note just 
below this gullet an elevation in which is a perpendicular 
slit, the glottis. This is the upper end of the laryngo- 
tracheal chamber, and the flaps within on either side of 
the slit are the vocal cords. 

Note at the posterior end of the body in the median 



THE GARDEN TOAD 7 

line an opening. This is the anal opening or amis. Note 
the general make-up of the toad. How do its arms com- 
pare with our own ? How do its fore feet (hands) differ 
from its hind feet ? Note that the body is covered by a 
tough enveloping membrane, the skin. In the skin are 
many glands which by their excretion keep it soft and 
moist. 

Internal structure — Technical Note.— With a fine pair of 
scissors make a longitudinal median cut through the skin of the 
venter from the anal opening to the angle of the lower jaw. Spread 
the cut edges apart and pin back in the dissecting-pan. 

Note the complex system of muscles which govern the 
movements of the tongue. Observe a number of pairs of 
muscles overlying the bones which support the arms. 
These are attached to the pectoral or shoulder -girdle. 
Note the large sheet of muscles covering the ventral 
aspect of the toad. These are the abdominal muscles, 
which consist of two sets, an outer and an inner layer. 
Note that posteriorly the abdominal muscles are attached 
to a bone. This is the pubic bone of the pelvic girdle 
which supports the hind legs. 

Technical Note. — With the scissors cut through the muscles of 
the body wall at the pubic bone and pass the points forward to the 
shoulder-girdle. Separate the bones of the shoulder-girdle and pin 
out the flaps of skin and muscle to right and left in the dissecting- 
pan (see fig. i). Cover the dissection with clear water or weak 
alcohol. 

Note two large conspicuous soft brown lobes of tissue. 
These form the liver, an organ which produces a secretion 
that assists in the process of digestion. Note just anterior 
to the liver and extending between its two lobes a pear • 
shaped organ, the heart, which may yet be pulsating. 
Are these pulsations regular ? How many occur in a 
minute ? The lower end or apex of the heart, ventricle, 
undergoes a contraction, forcing blood out into the blood- 



8 ELEMENTARY ZOOLOGY 

vessels. This is followed by a relaxation of the apex and 
a contraction of the basal portion, the auricle. The heart 
is surrounded by a delicate semi-transparent sac, the 
pericardium. The pericardium is filled with a watery 
fluid, body-lymph, which bathes the heart. Note between 
the lobes of the liver a small bladder-shaped transparent 
organ of a pinkish color. This is the gall-cyst, or gall- 
bladder, a reservoir for the bile, the secretion from the 
liver. Separate the lobes of the liver and note, beneath, 
the long convoluted tube which fills most of the body- 
cavity. This is part of the alimentary canal. Is the 
alimentary canal of uniform character ? The most anterior 
portion of the canal, the gullet or oesophagus, leads to a 
large U-shaped enlargement, the stomach. From the lower 
end of the stomach there extends a long, slender, very 
much convoluted tube, the small intestine, which is fol- 
lowed by a much larger one, the large intestine. This large 
intestine after one or two turns passes directly back into 
the rectum, which opens at last to the exterior through the 
anus. Note just ventral to the rectum a large thin-walled 
membranous sac. This is the urinary bladder which acts 
as a reservoir for the secretion from the kidneys. Notice 
a many-branched yellow structure with a glistening 
appearance, the fat-body {corpus adiposum). Now push 
liver and intestine to one side and note the pinkish sac-like 
bodies (perhaps filled with air), the lungs. The lungs are 
paired bodies which open into the laryngotracheal cham- 
ber. The toad takes air into its mouth through its 
nostrils, and then forces it, by a kind of swallowing action, 
through the laryngotracheal chamber into the lungs. 

Now lift the stomach and note in the loop between its 
lower end and the small intestine a thin transparent tissue. 
This is a part of the mesentery, which will be found to 
suspend the whole alimentary canal and its attached 
organs to the dorsal wall of the body. Note in the loop 



THE GARDEN TOAD 9 

of the stomach in the mesentery an irregular pinkish 
glandular structure which leads by a small duct into the 
intestine. This gland is the pancreas, and the duct is 
the pancreatic chut. From it comes a secretion which 
aids in the digestion of food. Near the upper end of the 
pancreas note a round nodular structure, generally dark 
red. This is the spleen, a ductless gland, the use of 
which is not altogether known. 

Make a drawing which will show as many of the organs 
noted as possible. 

Technical Note. — Pass two pieces of thread under the rectum 
near the pubic bone. Tie these threads tightly a short distance 
apart and then cut the rectum in two between the threads. Now 
carefully lift up the alimentary canal with attached organs (liver, 
etc.), and cut it off near the region of the heart. 

How is the heart situated with regard to the lungs ? 
The heart consists of a lower chamber with thick muscular 
walls, the tip, called the ventricle, and two upper thin- 
walled chambers, the right and left auricles. Can you 
make out these three chambers ? The purified blood from 
the lungs flows into the left auricle, while the venous 
blood from all over the body laden with its carbon dioxide 
enters the right auricle. From these two chambers the 
blood enters the ventricle. Here the pure and impure 
blood are mixed. From the ventricle the blood enters a 
large muscular tube on the ventral side of the heart. This 
is the conns arteriosus, which gives off three branches on 
each side; the anterior ones, the carotid arteries, supply 
the head, the next ones, the systemic arteries, or aorta y 
carry blood to the rest of the body, while the posterior 
vessels, the pulmonary arteries, go directly to the lungs 
and there break up into fine vessels (capillaries) where 
the carbon dioxide is given off and oxygen is taken from 
the air. From the lungs the blood returns through the 
pulmonary vein to the left auricle. Meanwhile the blood 



IO ELEMENTARY ZOOLOGY 

which has passed through the systemic arteries and body 
capillaries is collected again into other vessels going back 
to the heart; these are the veins, which empty into a large 
thin-walled reservoir, the sinus venosus> which in turn 
connects with the right auricle of the heart. Three large 
veins enter the sinus venosus, namely, two pre-caval veins 
at the anterior end, and a single post-caval vein at the 
posterior end. Trace out the larger arteries and veins 
from the heart to their division into or origin from the 
smaller vessels. 

Technical Note. — Carefully remove the heart together with 
the lungs. The lungs may be inflated by blowing into them through 
the laryngo-tracheal chamber with a quill and tying them tightly, 
after which they should be left for several days to dry. When 
perfectly dry, sections may be cut through them in various places 
with a sharp knife, and by this means a very good idea of the 
simple lung structure of the lower backboned animals can be ob- 
tained. With a sharp knife cut the heart open, beginning at the 
tip (ventricle) and cutting up through the conus arteriosus and 
the two auricles. Note the valves in the heart which separate 
the different compartments. 

Note on either side of the median line in the dorsal 
region a pair of reddish glandular bodies {the kidneys). 
From each kidney trace a tube {ureter*) posteriorly toward 
the region of the anus. The kidneys are the principal 
excretory organs of the body. The blood which flows 
through the delicate blood-vessels in the kidney gives up 
there much of its waste products. These pass out through 
small tubules of the kidneys into the ureters, which carry 
the wastes toward the anus. Along one side of each 
kidney may be seen a yellowish glistening mass, the 
adrenal body. 

In some of the specimens studied, the body cavity may 
be filled with thousands of little black spherical bodies. 
These are undeveloped eggs. They are deposited by the 
mother toad in the water in long strings of transparent 
jelly, which are usually wound around sticks or plant- 



THE GARDEN TOAD 



II 



stems at the bottom of the pond near the share. From 
these eggs the young toads hatch as tadpoles and in their 
nasal 

^ spheno-ethmoid 

digits 




- - calcaneum 



astragalus 

Yig. 2. — Skeleton of the garden toad. 

life-history pass through an interesting metamorphosis, 
fSee Chapter XII.) 



12 ELEMENTARY ZOOLOGY 

Technical Note. — The teacher should be provided with several 
well-cleaned skeletons of the toad in order that the bones may be 
carefully studied. Boil in a soap solution a toad from which most 
of the muscles and skin have been removed (see p. 452). Leave in 
this solution until the muscles are quite soft and then pick off all 
bits of muscles and tissue from the bones. If this is carefully done, 
the ligaments which bind the bones will be left intact and the 
skeleton will hold together. 

Note that the skeleton (fig. 2) consists of a head portion 
which is composed of many bones joined together to form 
a bony box, the skull; of a series of small segments, the 
vertebra, forming the vertebral column, which with the 
skull forms the axial skeleton; and of the appendicular 
skeleton, consisting of the bones of the fore and hind limbs. 
Note that the skull is composed of many bones joined 
together, some by sutures, while others are fused. Do 
the limbs attach directly to the axial skeleton ? The 
anterior limbs (arms) articulate with the pectoral or 
shoulder-girdle. The arms will be seen to be made up 
of a number of bones placed end to end. Note that the 
uppermost, the humerus, is attached to the pectoral 
girdle, while at its lower end it articulates with the 
radio-ulna. At the lower end of the radio-ulna is a small 
series of carpal bones which afford attachments for the 
slender finger-bones, the phalanges or digital bones. The 
bones of the leg are articulated with a closely fused set 
of bones, the pelvic girdle. The leg-bones, proceeding 
from the pelvic girdle, are named femur, tibio-fibida, 
tarsal bones, and phalanges or digits. To what bones of 
the arm do these correspond ? Determine the other 
principal bones of the skeleton by reference to figure 2. 

Technical Note. — In a specimen which has been macerated 
for some time in 20$ nitric acid dissect out the nervous system. 
Place the specimen in a pan ventral side uppermost and pin out. 
Carefully pick away the vertebrae and the roof of the mouth-cavity, 
thereby exposing the central nervous system, which will appear 
light yellow. 



THE GARDEN TOAD 13 

Examine the brain. In front of the true brain are the 
olfactory lobes, the nervous centre for the sense of smell. 
The brain itself is composed of several parts. The 
anterior portion consists of two elongated parts, the 
cerebral hemispheres ; just back of these are the optic lobes 
or midbrain, consisting of two short lobes, which are fol- 
lowed by the small cerebellum, which in turn is followed 
by a long part, the medulla oblongata, which runs imper- 
ceptibly into the long dorsal nerve, the spinal cord. Note 
the large optic nerves running out to each eye. How far 
backward does the spinal cord extend ? Note the many 
pairs of nerves given off from the brain and spinal cord. 
These nerves branch and subdivide until they end in very 
fine fibres. Some end in the muscle-fibres, and through 
them the central nervous system innervates the muscles. 
These are motor endings. Still others pass to the surface 
and receive impressions from the outside. These last are 
sensory endings. Note that the spinal nerves arise from 
the spinal cord by two roots, an anterior or ventral, and 
a posterior or dorsal root. Trace the principal spinal 
nerves to the body-parts innervated by them. These 
nerves are numbered as first, second, etc., according to 
the number of the vertebrae (counting from the head back- 
ward) from behind which they arise. 



CHAPTER III 

THE STRUCTURE AND FUNCTIONS OF THE 

ANIMAL BODY 

Organs and functions. — The body of the toad is com- 
posed of various parts, such as the lungs, the heart, the 
muscles, the eyes, the stomach, and others. The life of 
the toad consists of the performance by it of various 
processes, such as breathing, digesting food, circulating 
blood, moving, seeing, and others. These various 
processes are performed by the various parts of the body. 
The parts of the body are called organs, and the processes 
(or work) they perform are called their functions. The 
lungs are the principal organs far the function of breath- 
ing; the heart, arteries and veins are the organs which 
have for their function the circulation of the blood ; the 
principal organ concerned in the digestion of food is the 
alimentary canal, the function of seeing is performed by 
the organs of sight, the eyes, and so one might continue 
the catalogue of all the organs of the body and of all the 
functions performed by the animal. 

The animal body a machine. — The whole body of the 
toad is a machine composed of various parts, each part 
with its special work or business to do, but all depending 
on one another and all co-operating to accomplish the total 
work of living. The locomotive engine is a machine 
similarly composed of various parts, each part with its 
special work or function, and all the parts depending on 
one another and so working together as to perform satis- 

14 



STRUCTURE AND FUNCTIONS OF THE ANIMAL BODY 15 

factorily the work for which the locomotive engine is 
intended. An important difference between the locomo- 
tive engine and the toad's bodv is that one is a lifeless 
machine and the other a living machine. But there is a 
real similarity between the two in that both are composed 
of special parts, each part performing a special kind of 
work or function, and all the parts and functions so fitted 
together as to form a complex machine which successfully 
accomplishes the work for which it is intended. And this 
similarity is one which should help make plain the funda- 
mental fact of animal structure and physiology, namely, 
the division of the body into numerous parts or organs, 
and the division of the total work of living into various 
processes which are the special work or functions of the 
various organs. 

The essential functions or life-processes. — The toad 
has a great many different special parts in its bod}'. Its 
body is very complex. It performs a great many differ- 
ent functions, that is, does a great many different things 
in its living. And the structure and life of most of the 
other animals with which we are familiar are similarly 
complex: a fish, or a rabbit, or a bird has a body com- 
posed of many different parts, and is capable of doing 
many different things. Are all animals similarly complex 
in structure, and capable of doing such a great variety of 
things ? We shall find that the answer to this question 
is No. There are many animals in which the body is 
composed of but a few parts, and whose life includes the 
performance of fewer functions or processes than in the 
case of the toad. There are many animals which have 
no eyes nor ears nor other organs of special sense. 
There are animals without legs or other special organs of 
locomotion ; some animals have no blood and hence no 
heart nor arteries and veins. But in the life of every 
animal there are certain processes which must be per- 



16 ELEMENTARY ZOOLOGY 

formed, and the body must be so arranged or composed 
as to be capable of performing these necessary life- 
processes. All animals take food, digest it, and assimi- 
late it, that is, convert it into new body substance; all 
animals take in oxygen and give off carbonic acid gas; 
all animals have the power of movement or motion (not 
necessarily locomotion) : all animals have the power of 
sensation, that is, can feel; all animals can reproduce 
themselves, that is, produce young. These are the 
necessary life-processes. It is evident that the toad could 
still live if it had no eyes. Seeing is not one of the 
necessary functions or processes of life. Nor is hearing, 
nor is leaping, nor are many of the things which the toad 
can do ; and animals can exist, and do exist, without any 
of those organs which enable the toad to see and hear and 
leap. But the body of any animal must be capable of 
performing the few essential processes which are necessary 
to animal life. How surprisingly simple such a body can 
be will be later discovered. But in most animals the 
body is a complicated object, and is able to do many 
things which are accessory to the really essential life- 
processes, and which make its life complex and elaborate. 



CHAPTER IV 
THE CRAYFISH {Cambarus sp.) 

LABORATORY EXERCISE 

Technical Note. — The crayfish, or crawfish, is found in most of 
the fresh-water ponds and streams of the United States. (It is not 
found east of the Hoosatonic River, Mass. In this region the lob- 
ster may be used. On the Pacific coast the crayfishes belong to the 
genus Astacus.) Crayfishes may be taken by a net baited with dead 
fish, or they may be caught in a trap made from a box with ends 
which open in, and baited with dead fish or animal refuse of any 
sort. This box should be placed in a pond or stream frequented 
by crayfish. If possible the student should study the living animal 
and observe its habits. Crayfish which are to be kept alive should be 
placed in a moist chamber in a cool place. They will keep for a 
longer time in a moist chamber than in water. Some fresh specimens 
should be injected by the teacher for the study of the circulatory 
svstem. A watery solution of coloring matter or, better, of an in- 
jecting mass of gelatine (see p. 451" is injected into the heart 
through the needle of a hypodermic syringe. For the purpose of 
injecting, a small bit of the shell may be removed from the cephalo- 
thorax above the heart. Specimens which are to be kept for some 
time should be placed in alcohol or \ r c formalin. 

External structure (fig. 3). — Place a specimen in a 
pan for study. Note that the body, which of course differs 
much in shape from that of the toad, is also unlike that of 
the toad in being covered by a hard calcareous cxoskclcton, 
which acts as a covering for the soft parts and also as a 
place of attachment for the muscles, just as the internal 
skeleton does in the case of the toad, --rfhe body is com- 
posed of an anterior part, the cepkalothorax, and a 
posterior part, the abdomen. The cephalothorax is covered 
above and on the sides by the carapace, which is divided 
into parts corresponding to the head and thorax of the 

17 



ELEMENTARY ZOOLOGY 



antennule 



opening of green gland 



maxilliped 



thorax 



genital aperture -m~~ 




'uropod 
^x—telson 



F IG . 3. —Ventral aspect of crayfish (Cambarus sp.), with the appendages of 

one side disarticulated. 



THE CRAYFISH *9 

toad by the transverse cervical suture. The abdomen 
is composed of segments. How many ? The flattened 
terminal segment is called the telson. Is the cephalo- 
thorax composed of segments ? Where is the mouth of 
the crayfish ? Where is the anal opening ? 

At the anterior end of the cephalothorax note a sharp 
projection, the rostrum. Where are the eyes ? Remove 
one of them and examine its outer surface with a micro- 
scope. A bit of the outer wall should be torn off and 
mounted on a glass slide. Note that it is made up of a 
great many little facets placed side by side. Each of 
these facets is the external window of an eye element or 
ommatidium. An eye composed in this way is called a 
compound eye. In front of the eyes note two pairs of 
slender many-segmented appendages. The shorter pair, 
the antennules, are two-branched. Remove one of them 
and note at its base a small slit along the upper surface. 
This slit opens into a small bag-like structure which con- 
tains fine sand-grains. The bag is protected by a series 
of fine bristles along the edge of the slit. This bag-like 
structure is believed to be an auditory organ. The longer 
pair of appendages are the antennce, and in the fine hair- 
like projections upon the joints is believed to be located 
the sense of smell. Thus it will be seen that the sense- 
organs of the crayfish, like those of the toad, are located 
on the head. Beneath the basal portion of each antenna 
there is a flat plate-like projection, at the base of which 
on the upper edge will be noted a small opening, the 
exit of the kidney, or green gland. 

Make a drawing of the surface of part of an eye ; also 
of an antennule ; and of an antenna. 

Technical Note. — Stick one point of the scissors under the 
posterior end of the carapace on the right side, and cut forward, 
thus exposing a large cavity, the gill-chamber. Remove all of the 
mouth-parts, legs and abdominal appendages from the right side, 
being careful to leave the fringe-like parts, the gills, attached to 



20 ELEMENTARY ZOOLOGY 

their respective legs. Place all of the appendages in order on a 
piece of cardboard. 

Examine the abdominal appendages, called pleopods, 
or swimming feet. How many pairs are there ? Each 
is composed of a basal part, the protopodite, and two 
terminal segments, an inner one, the endopodite, and an 
outer, the exopodite. In the males the first and second 
pleopods of the abdomen are larger and less flexible than 
the others. In the female the pleopods serve to carry 
the eggs and the first two pairs are very small or absent. 
Note the last set of abdominal appendages. These are 
the nropods, which together with the telson form the tail. 

Make a drawing of the pleopods of one side. 

Examine the appendages of the cephalothorax. Like 
the appendages of the abdomen the typical composition 
of each includes a protopodite, an exopodite and an 
endopodite, but some of these appendages are much 
modified, and show a loss of one of these parts, or the 
addition of an extra part. The cephalothoracic appen- 
dages may be divided into three groups, an anterior group 
of three pairs of mouth-parts (belonging to the head) of 
which the first pair is the mandibles and the others are the 
maxillcz; a second group of three pairs of foot-jaws or 
maxillipeds, belonging to the thorax, and a third group of 
five pairs of walking-legs. The mandibles, lying next to 
the mouth-opening, are hard and jaw-like and lack the 
exopodite ; the first maxillae are small and also lack the 
exopodite; the second maxillae have a large paddle-like 
structure which extends back over the gills on each side 
within the space, the branchial chamber, above the gills. 
It is by means of this paddle-like structure (the scaphog- 
nathite) that currents of water are kept up through the 
gill-chambers. The maxillipeds increase in size from 
first to third pair. Each pair of walking-legs except the 
last bears gills. These gills are the organs by which 



THE CRAYFISH 21 

the blood is purified. The blood of the crayfish flows into 
the large vessels on the outer sides of the gill and thence 
into the fine vessels in the little leaf-like lamellae. At the 
same time the air which is mixed with the water bathing 
the gills passes freely through the thin membranous walls 
of these lamellae and blood-vessels, and the blood gives 
off its carbonic acid gas to the water and takes up oxygen 
from the air in the w r ater. Thus it will be seen that the 
office of the gill is like that of the lung in the toad, 
namely, to act as an organ for the elimination of carbonic 
acid gas and the taking up of oxygen. 

Note the pincer-like appendages of the first pair of legs. 
These pincers are the cliclce, with which food is torn into 
bits and placed in the mouth. In the basal segment of 
each of the last pair of legs of the male note the genital 
pore. In the female the genital pores are in the basal 
segments of the next to last pair of legs. Is the crayfish 
bilaterally symmetrical ? Note the repetition of parts in 
the crayfish, that is, the recurrence of similar parts in 
successive segments. This serial repetition of parts among 
animals is called metemerism. 

Internal Structure (fig. 4).— Technical Note.— With a pair 
of scissors cut through the dorsal wall of the cephalothorax into the 
body-cavity. Cut the body-wall away from both sides and remove 
the middle portion. 

At the anterior end of the cephalothorax note the large 
membranous sac, the stomach. Attached to each end of 
this are sets of muscles which control its movements. 
To the right and left of the stomach notice attached to 
the shell large muscles which connect by stout ligaments 
at their lower ends with the mandibles. Note a yellow 
fringe-like structure, the digestive gland, which fills most 
of the region about the stomach. It connects by a pair 
of small tubes, the bile-dticts, with the alimentary canal. 
Within the posterior portion of the cephalothorax note a 



22 



ELEMENTARY ZOOLOGY 











JO 








s* ^ 








s o 








^ CO 








* 1 














*"*•* »^o 








5 « 








S § 








"5* *5 








S S 






£ 






eo 








s 

e 


"■•■o 

3 




^ 




8 




~3 


s 


o 




^» 


•tS 1 




CO 


at, 






C3 


> 






«K 










^v J 1 






e 


x i^"~ 






>^> 


\ 








-<> 


N 
N 

\ 
<3 


i 




"C: 










o 




CO 






<3 




O 






s 


CO 








•»o 






sL 




CO 


"co 


\ m 






<^> 


■ : f 




•o 


■*■-* 


- - -Oil 




•<s> 








*» 




HI 




O 




- II 




>> 


~-~ — JiJL 




a. 


-'$» 






^ 


"** i 


' 






















c?V 






1 


, 


S 






i 




^ 






[ 








<: 






"s 




-*«3 „ 






a 






i 








1 

<2 


I 






o 
« 




t* 

£ 


£ 
o 

to 
CO 


° / it 

r \ 

CO 




„g 




f 4 












"& 




„"' 




s 


' 


,*' 






* 


•ft 














C* ^ 



e 



u 

u 

o 



T3 

'So 

c 

el 

a; 



s 

£ 



s 

Pin 



THE CRAYFISH 23 

pentagonal sac, the heart, contained within a delicate 
membrane, the pericardium. Remove the pericardium 
and note a pair of dorsal openings into the heart, called 
ostia. (There are also two lateral pairs and a ventral 
pair of ostia.) Xote passing anteriorly from the heart 
along the median line to the eyes a blood-vessel, the 
ophthalmic artery. Arising from the anterior portion of 
the heart are the antennary arteries, running to the 
antennae. Yet another pair running anteriorly from the 
heart to the stomach and digestive glands are called the 
hepatic arteries. From the posterior end of the heart 
arises the dorsal abdominal artery, running back to the 
telson. Below this arises the sternal arterv, which will 
be seen later. 

In the region below the heart are located the reproduc- 
tive organs. The}' are whitish glandular masses from 
each of which runs a tube which opens at the base of the 
last pair of walking-legs in the male, and at the base of 
the third pair of walking-legs in the female. 

Technical Note. — Cut longitudinally through the dorsal wall 
of the abdomen on either side of the median line and remove the 
piece of shell. 

Xote the powerful muscles within which flex and extend 
the abdomen. By a rapid contraction of these muscles 
the tail is brought beneath the body, propelling the animal 
strongly backwards. When the crayfish crawls it gen- 
erally goes forward, but in swimming it reverses this 
direction. 

Make a drawing showing, in their natural position, the 
internal organs which have been studied. 

Examine the alimentary canal for its whole length. 
Xote that the large bladder-shaped stomach is attached 
to the mouth-opening by a short tube. What part of the 
canal is this ? From the posterior end of the stomach is 
a short thick-walled part, the small intestine, followed by 



24 ELEMENTARY ZOOLOGY 

a long straight tube, the large intestine, which opens to 
the exterior through the anus. 

Technical Note. — Remove the alimentary canal, detaching it 
from the anal end first, and working forward. 

Cut the stomach open. Note an anterior portion, the 
cardiac chamber, and a smaller posterior portion, the 
pyloric chamber. Examine its inner surface. What do 
you find here ? This structure is called the gastric mill. 
Food, which for the most part consists of any dead 
organic matter, is chewed by the "stomach-teeth" into 
fine bits, and is then passed into the pyloric chamber. It 
is here that the digestive glands empty their secretion into 
the food. These glands have the same office as have the 
liver and pancreas combined in the toad, and so they are 
often called the liepato-pancreas. When the stomach has 
been removed there will be noted in the anterior portion 
of the body paired, flattened bodies, already mentioned, 
which connect with openings at the base of each of the 
antennae by means of wide thin-walled sacs, the ureters. 
These organs are the kidneys, or green glands. Their 
office is similar to that of the kidneys in the toad, namely, 
the elimination of waste from the body. 

Technical Note.— Carefully remove all of the alimentary canal, 
digestive glands, and reproductive organs. This process will expose 
the floor of the cephalothorax. Now cut away from either side the 
horny floor or bridge at the bottom of the cephalothorax. If the 
specimen has not already been immersed, place it in clear water for 
further dissection. 

The foregoing dissection will expose the central nervous 
system. It extends as a series of paired ganglia con- 
nected by a double nerve-cord along the ventral median 
line from the oesophagus to the last segment of the 
abdomen. From what points do the lateral nerves arise ? 
Anteriorly the double nerve-cord divides, the two parts 



THE CRAYFISH 25 

passing upward on each side of the oesophagus, where they 
again meet to form the supra-oesophageal ganglion or 
brain. Where do the nerves run which rise from the 
brain ? What is the difference between the position of 
the central nervous system in the crayfish and in the toad ? 

Make a drawing of the nervous system. 

Just beneath the nerve-cord note a blood-vessel ex- 
tending the length of the body. This is the sternal 
artery, which arises from the posterior end of the heart 
and passes ventrally at one side of the alimentary canal 
and between the nerve-cords. Here the sternal artery 
divides into an anterior and a posterior branch, from 
which lesser branches are given off to each one of the 
appendages. The various arteries running to all parts of 
the body finally pour out the blood into the body-cavity, 
where it flows freely in the spaces among the various tissues 
and organs. After the blood has bathed the body tissues 
it flows to the gills on either side, passing up the outer 
side of the gill through delicate thin-walled vessels, where 
it is oxygenated as has already been described. From 
the gills the purified blood flows back on the inner side 
through a large chamber, sinus, into the pericardium, 
through the ostia of the heart, whence it is driven into the 
arteries once more. This sort of a circulatory system in 
which the blood in places is not enclosed in a definite 
vessel is known as an open system. In the toad we find 
the blood in a closed system, i.e., arteries leading into 
capillaries which in turn lead into veins, in no case allow- 
ing the blood to pass freely through the spaces of the 
body. 



CHAPTER V 

THE MODIFICATION OF ORGANS AND FUNC- 
TIONS 

Differences between crayfish and toad. — In the dis- 
section of the crayfish one of the most important things in 
the study of zoology has been learned. It is plain that 
the crayfish has a body composed, like the toad's, of 
parts or organs, and that most of these organs, although 
differing much in appearance and actual structure from 
those of the toad, correspond to similarly named organs 
of the toad, and perform the same functions or processes, 
although with many striking differences, essentially in the 
same way as in the toad. But the structure of the body 
is very different in the two animals. The toad has an 
internal body skeleton to which the muscles are attached, 
and a soft, yielding, outer body-covering or skin; the 
crayfish has no internal skeleton, but has its body covered 
by a horny, firm body-wall to which the muscles are 
attached. The toad has its main nervous chain lying just 
beneath the dorsal wall of the body; the crayfish has its 
main nervous chain lying just above the ventral wall of 
the body. The toad has lungs and takes up oxygen from 
the air of the atmosphere ; the crayfish has gills and takes 
up oxygen from the air which is mixed with the water. 
The toad has a single pair of jaws; the crayfish has 
several pairs of mouth-parts. The toad has four legs 
fitted for leaping ; the crayfish has numerous legs fitted 
for crawling or swimming. The crayfish's body is com- 

26 



THE MODIFICATION OF ORGANS AND FUNCTIONS 27 

posed of a series of body-rings or segments; the toad's 
body is a compact apparently unsegmented mass. The 
toad has eyes each with a single large lens and capable 
of moving in the head and of changing their shape and 
hence their focus; the crayfish's eyes are immovable and 
have a fixed focus, and are composed of hundreds of tiny 
eyes each with lens and special retina of its own. And 
so a long list of differences might be gone through with. 

Resemblances between toad and crayfish. — But on the 
other hand there are many resemblances — resemblances 
both in structure and life-processes or physiology. Both 
toad and crayfish have organs for the prehension of food, 
its digestion and its assimilation. And these organs, the 
organs of the digestive system, while differing in details 
are alike in being composed principally of a long tube, 
the alimentary canal, running through the body, open 
anteriorly for the taking in of food, and open posteriorly 
for the discharge of indigestible useless matter Both 
alimentary canals are divided into various special regions 
for the performance of the various special processes con- 
nected with the digestion and assimilation of food. Each 
is adapted for the special kind of food which it is the habit 
of the particular animal to take. The two sets of organs 
are essentially alike and have the same essential function 
or life-process to perform. But this process differs in the 
details of its performance, and the organs which perform 
this function and which constitute the digestive system of 
each are modified to suit the special habits or kind of life 
of the animal. 

Both toad and crayfish have a heart with blood-vessels 
leading from it. In the case of the toad the heart is more 
complex than in the crayfish, and the system of blood- 
vessels is far more extensive and elaborate. But the heart 
and blood-vessels in both animals subserve the same pur- 
pose ; their function is the circulation of the blood, this 



28 ELEMENTARY ZOOLOGY 

being the means by which oxygen and food are carried 
to all growing or working parts of the body, and by 
which carbonic acid gas and other poisonous waste 
products are brought away from these parts. But this 
function differs somewhat in its performance in the two 
animals, and the organs which perform the function are 
correspondingly modified in structural condition. 

Both toad and crayfish have organs for respiration, that 
is, for breathing in oxygen and breathing out carbonic 
acid gas. But the toad takes its oxygen from the 
atmosphere about it; its respiratory organs are the 
lungs, the sac-like tube leading to the mouth, and 
the external openings for the ingress and exit of the 
gases. The crayfish, living mostly in the water, takes 
its oxygen from the air which is mechanically mixed 
with the water. Its respiratory organs are its gills. 
There is a great difference, apparently, in the structural 
conditions of the organs of respiration in the two animals. 
As a matter of fact the difference is less great than, at 
first sight, appears to be the case. The lungs of the toad 
are composed primarily of a thin membrane, in the form 
of a sac, richly supplied with blood-vessels. Air is 
brought to this thin respiratory membrane and by osmosis 
the oxygen passes through the membrane and through 
the thin walls of the fine blood-vessels, and is taken up 
by the blood. At the same time the carbonic acid gas 
brought by the blood to the lungs from all parts of the 
body is given up by it and passes through the membranes 
in order to leave the body. The air comes in contact 
with the respiratory membrane (which is situated inside 
the body) by means of a system of external openings and 
a conducting chamber, and by these same openings and 
chamber the carbonic acid gas leaves the body. In the 
crayfish the gills are nothing else than a large number of 
small flattened sacs each composed of a thin membrane 



THE MODIFICATION OF ORGANS AND FUNCTIONS 29 

richly supplied with blood-vessels. This respiratory mem- 
brane is not, in the crayfish, situated inside the body, but 
on the outer surface, although protected by being in a sort 
of pocket with a covering flap, and it comes into immediate 
contact with the air held in the w r ater which freely bathes 
the gills. By osmosis the oxygen of this air passes in 
through the gill-membranes, while the carbonic acid gas 
brought by the blood passes out through them. Exactly 
the same exchange of gases is accomplished as in the 
toad. But because of the great difference in the conditions 
of life of the toad and crayfish, one living in water, the 
other living out of water, the character of the performance 
of the function of respiration, and correspondingly the 
structural condition of the organs performing this function, 
are strikingly different. 

Modification of functions and structure to fit the 
animal to special conditions of its life. — As has been 
done with the organs of digestion, circulation, and 
respiration, so we might compare the other organs of the 
crayfish and the toad. There would be found not only 
many very marked differences between organs which have 
the same general function in the two animals, but we 
should find also numerous organs in the toad which are 
not present at all in the crayfish, and conversely; and this 
means, of course, that the toad can do numerous things, 
perform numerous functions, which the crayfish cannot, 
and, conversely, that the crayfish does some things which 
the toad cannot. But both of these animals agree in 
possessing in common the capability of performing those 
processes such as taking food, breathing, reproducing, 
etc., to which attention has been called as being indis- 
pensable to all animal life. These processes, however, 
are performed by the two animals in different ways and 
the organs for the performance of these processes, although 
at very bottom essentially alike, are in outer and super- 



3° ELEMENTARY ZOOLOGY 

ficial details of position, appearance and general structure 
markedly different. Animals are fitted to live in different 
places amid different surroundings by having their bodies 
modified and the performance of their life-processes modi- 
fied to suit the special conditions of their life. 

Vertebrate and invertebrate. — In selecting the toad 
and the crayfish as the first animals to study and to com- 
pare with each other, we have chosen representatives of 
the two great groups into which the complexly organized 
animals are divided, viz., the group of backboned or 
vertebrate animals, and the group of backboneless or 
invertebrate animals. To the vertebrates belong all those 
which have an internal bony skeleton (and a few without 
such a skeleton) and which have also an arrangement of 
body-organs on the general plan of the toad's body. A 
conspicuous feature of this arrangement is the situation of 
the spinal cord or main great nerve-trunk along the back 
or dorsal wall of the animal, and inside of a backbone. 
All the fishes, batrachians (frogs, toads, salamanders, 
etc.), reptiles (snakes, lizards, alligators, etc.), birds, and 
mammals (quadrupeds, whales, seals, etc.) belong to the 
vertebrates. The backboneless or invertebrate animals 
have no internal bony skeleton and have their main nerve- 
trunk usually along the ventral wall of the body, some- 
times in a circle around the moiith, but never in a back- 
bone. To the invertebrates belong all insects, lobsters, 
crabs, clams, squids, snails, worms, starfishes and sea- 
urchins, corals and sponges, altogether a great host of 
animals, mostly small. 



CHAPTER VI 

AMCEBA AND PARAMCECIUM 

LABORATORY EXERCISE 

AmCBba. — Technical Note. — Amoebae are found in stagnant 
pools of water on the dead leaves, sticks and slime at the bottom. 
To obtain them, collect slime and water from various puddles in sepa- 
rate bottles and take them to the laboratory. Place a small drop of 
slime on a slide under a cover-glass. Examine under the low power 
first and note any small transparent or opalescent objects in the 
field. Examine these objects with the higher power and note that 
some are mere granular jelly-like specks, which slowly (but con- 
stantly) change their form. These are Amoeba. 

A teacher of zoology recommends the following method of obtain- 
ing a large supply of Amoeba : "For rearing Amaebce place two or 
three inches of sand in a common tub, which is then filled with 
water and placed some feet from a north window ; three or four 
opened mussels, with merest trace of the mud from the stream in 
which they are taken, are partially buried in the sand and a hand- 
ful of Nitella and a couple of crayfish cut in two are added ; as 
decomposition goes on a very gentle stream is allowed to flow into 
the tub, and after from two to four weeks abundant Amoebae are to 
be found on the surface of the sand and in the scum on the sides of 
the tub ; small Amoebae appear at first, and later the large ones." 

Having found an Amoeba (fig. 5) note its irregular 
shape, and if it moves actively observe its method of mov- 
ing. How is this accomplished ? The viscous, jelly-like 
substance which composes the whole body of an Amceba 
is called protoplasm. The little processes which stick 
out in various directions are the " false feet" {pseudo- 
podia). Note that the outer portion, the ectosarc, of the 
protoplasmic body is clear, while the inner, the endosarc, 
is more or less granular in structure. Has Amoeba a 
definite body-wall ? Do the pseudopodia protrude only 

31 



32 



ELEMENTARY ZOOLOGY 



from certain parts of the body ? Within the endosarc 
note a clear globular spot which contracts and expands, 
or pulsates, more or less regularly. This is the contrac- 
tile vacuole. Note the small granules which move about 
within the endosarc. These are food-particles which 




Fig. 5. — Amoeba sp. ; showing the forms assumed by a single individual in 
four successive changes. (From life.) 



have been taken in through the body-wall. Note how 
pseudopodia flow about food-particles in the water and 
how these are digested by the protoplasm. If an Amoeba 
comes into contact with a particle of sand, note how it at 
once retreats. Note within the endosarc an oval trans- 
parent body which shows no pulsations. This is the 



AMCEBA AND PARAMECIUM 33 

nucleus, a very complex little structure of great impor- 
tance in the make-up of Amoeba. 

Note that Amoeba has no mouth or alimentary canal; 
no nostrils or lungs, no heart or blood-vessels, no mus- 
cles, no glands. It is an animal body not made up of 
distinct organs and diverse tissues. Its whole body is a 
simple minute speck of protoplasm, a single animal cell. 
But it takes in food, it moves, it excretes waste matter 
from the body, is sensitive to the touch of surrounding 
objects, and, as we may be able to see, it can reproduce 
itself, i.e., produce new Amoeba. Amoeba is the simplest 
living animal. 

It is only rarely that we can find an Amoeba actually 
reproducing. The process, in its gross features, is very 
simple. First the Amoeba draws in all of its pseudopodia 
and remains dormant for a time. Next, certain changes 
take place in the nucleus, which divides into equal por- 
tions, one part withdrawing to one end of the protoplasmic 
body, the other to the opposite end. Soon the body pro- 
toplasm itself begins to divide into two parts, each part 
collecting about its own half of the nucleus. Finally the 
two halves pull entirely away from each other and form 
two new Amoeba, each like the original, but only half as 
large. This is the simplest kind of reproduction found 
among animals. 

Amoeba continue to live and multiply as long as the 
conditions surrounding them are favorable. But when 
the pond dries up the Amoeba in it would be exterminated 
were it not for a careful provision of nature. When the 
pond begins to dry up each Amoeba contracts its pseudo- 
podia and the protoplasm secretes a horny capsule about 
itself. It is now protected from dry weather and can be 
blown by the winds from place to place until the rains 
begin, when it expands, throws off the capsule and com- 
mences active life again in some new pond. 



34 ELEMENTARY ZOOLOGY 

The Slipper Animalcule {Paramoecium sp.) — technical 

Note. — Paramcecia can be secured in most pond water where 
leaves or other vegetation are decaying. However, if specimens 
are not readily secured place some hay or finely cut dry clover in a 
glass dish, cover with water and leave in the sun for several days. 
In this mixture specimens will develop by thousands. Place a drop 
of water containing Paramaccia on a slide with cover-glass over it. 
Using a low power, note the many small animals darting hither and 
thither in the field. Run a thin mixture of cherry gum in water 
under the cover-glass. In this mixture they can be kept more quiet 
and be better studied. 

How does Paramoecium (fig. 6) differ from Amoeba in 
form and movement ? Has the body an anterior and a 
posterior end ? The delicate, short, thread-like processes, 
on the surface of the body, which beat about very rapidly 
in the water are called cilia, and they are simply fine 
prolongations of the body protoplasm. What is their 
function ? Note a fine cuticle covering the body. Note 
also many minute oval sacs lying side by side in the 
ectosarc. These are called trichocysts and from each a 
fine thread can be thrust out. 

Note on one side, beginning at the anterior end, the 
buccal groove leading into the interior through the gullet. 
Observe also that by the action of the cilia in the buccal 
groove food-particles are swept into the gullet. Rejected 
or waste particles are ejected from the body occasionally. 
Where ? Note about midway of the Paramoecium an 
ovoid body with a smaller oval one attached to its side, 
the forme** being the macronuclcus, the latter the micro- 
nucleus. Note that there are two contractile vacuoles in 
the Paramoecium; also that the food-vacuoles have a 
definite course in their movement inside the endosarc. 

Make a drawing of a Paramoecium. 

In comparing Paramoecium with Amoeba it is apparent 
that the body of the first is less simple than that of the 
second. The definite opening for the ingress of food, the 
two nuclei, the fixed cilia, and the definite cell-wall giving- 



AMOEBA AND PARAMECIUM 



35 



a fixed shape to the body, are all specializations which 
make Par amoecium more complex than Amoeba. But the 
whole body is still composed of a single cell, and there 
is, as in Amoeba, no differentiation of the body-substance 
into different tissues, and no arrangement of body-parts 
as systems of organs. 

Par amoecium may occasionally be found reproducing. 
This process takes place very 
much as in Amoeba. The animal 
remains dormant for a while, the 
micronucleus then divides, the 
macronucleus elongates and 
finally divides in two, the proto- 
plasm of the body becomes con- 
stricted into two parts, each part 
massing itself about thewithdrawn 
halves of the macro- and micro- 
nuclei, and lastly the whole breaks 
into two smaller organisms which 
grow to be like the original. 
After multiplication or reproduc- 
tion has gone on in this way for 
numerous generations (about one 
hundred), a fusion of two Para- 
moecia seems necessary before 
further divisions take place. This 
process of fusion, called conjuga- 
tion, may be noted at some sea- 
sons. Two Paramcvcia unite with 
their buccal grooves together, 
part of the macronucleus and micronucleus of each passes 
over to the other, and the mixed elements fuse together 
to form a new macro- and micronucleus in each half. 
The conjugating Paramoecia now separate, and each 
divides to form two new individuals. 




Fig. 6. — Paramceciuj?i sp. ; 
buccal groove at right. (From 
life.) 



CHAPTER VII 

THE SINGLE-CELLED ANIMAL BODY.— PRO- 
TOPLASM AND THE CELL 

The single-celled body. — The study of Amoeba and 
Paramoecium has made us acquainted with an animal body 
very different from that of the toad or the crayfish. These 
extraordinarily minute animals have a body so simple in 
its composition, compared with the toad's, that if the 
toad's body be taken for the type of the animal body, 
Amoeba might readily be thought not to be an animal at 
all. The body of Amoeba is not composed of organs, each 
with a particular function or work to perform. Whatever 
an Amoeba does is done, we may say, with its whole body. 
But as we learn the things that this formless viscid speck 
of matter does, we see that it is truly an animal; that it 
really does those things which we have learned are the 
necessary life-processes of an animal. Amoeba takes up 
and digests food composed of organic particles; it has the 
power of motion ; it knows when its body comes in con- 
tact with some external object, that is, it can feel or has 
the power of sensation. Amoeba takes in oxygen and 
gives out carbonic acid gas, and it can produce new in- 
dividuals like itself, that is, it has the power of reproduc- 
tion. But for the performance of these various life-pro- 
cesses or functions it has no special parts or organs, no 
mouth or alimentary canal, no lungs or gills, no legs, no 
special reproductive organs. We have here to do with one 
of the "simplest animals. ' ; With a minute, organless, 

36 



THE SINGLE-CELLED ANIMAL BODY 37 

soft speck of viscous matter called protoplasm for a body, 
the simplest structural condition to be found among living 
beings, Amoeba nevertheless is capable of performing, in 
the simplest way in which they may be performed, those 
processes which are essential to animal life. 

Paramoecium has a body a little less simple than 
Amoeba. The food-particles are taken into the body 
always at a certain spot; this might be spoken of as a 
mouth. And the body has some special locomotory 
organs, if they may be so called, in the presence of the 
cilia. The body, too, has a definite shape or form. 
But, as in Amoeba, there is no alimentary canal, nor 
nervous system, nor respiratory system, nor reproductive 
system. The whole body feels and breathes and takes 
part in reproduction. 

A long jump has been made from the toad and crayfish 
to Amoeba and Paramoecium; from the complex to the 
simplest animals. But, as will later be seen, the great 
difference between the bodies of these simplest animals 
and those of the highly complex ones is only a difference 
of degree ; there are animals of all grades and stages of 
structural condition connecting the simplest with the most 
complex. When animals are studied systematically, as 
it is called, we begin with the simplest and proceed from 
them to the slightly complex, from these to the more 
complex, and finally to the most complex. There are 
hundreds of thousands of different kinds of animals, and 
they represent all the degrees of complexity which lie 
between the extremes we have so far studied. 

The cell. — The characteristic thing about the body of 
Amoeba and Paramoecium and the other "simplest 
animals " — for there are many members of the group of 
i ' simplest animals," or Protozoa — is that it is com- 
posed, for the animal's whole lifetime, of a single cell. 
A cell is the structural unit of the animal body. As 



3 8 ELEMENTARY ZOOLOGY 

will be learned in the next exercise, the bodies of all 
other animals except the Protozoa, the simplest animals, 
are composed of many cells. These cells are of many 
kinds, but the simplest kind of animal cell is that shown 
by the body of an Amoeba, a tiny speck of viscous, nearly 
colorless protoplasm without fixed form. The protoplasm 
composing the cell is differentiated to form two parts or 
regions of the cell, an inner denser part, called the 
nucleus, and an outer clearer part, called the cytoplasm. 
Sometimes, as in the Paramoecium, the cell is enclosed by 
a cell-wall which may be simply a denser outer layer of 
the cytoplasm, or may be a thin membrane secreted by 
the protoplasm. Thus the cell is not what its name 
might lead us to expect, typically cellular in character; 
that is, it is not (or only rarely is) a tiny sac or box of 
symmetrical shape. While the cell is composed essen- 
tially of protoplasm, yet it may contain certain so-called 
cell-products, small quantities of various substances pro- 
duced by the life-processes of the protoplasm. These 
cell-products are held in the protoplasmic body-mass of 
the cell, and may consist of droplets of water or oil or resin, 
or tiny particles of starch or pigment, etc. The cell 
cannot be said to be composed of organs, because the 
word organ, as it is commonly used in the study of an 
animal, is understood to mean a part of the animal body 
which is composed of many cells. But the single cell 
can be somewhat differentiated into parts or special 
regions, each part or special region being especially 
associated with some one of the life-processes. In 
Paramoecmin^ for example, the food is always taken in 
through the so-called mouth-opening; the fine proto- 
plasmic cilia enable the cell to swim freely in the water, 
the waste products of the body are always cast out through 
a certain part, and so on. But this is a very simple sort 
of differentiation, and the whole body is only one of those 



THE SINGLE-CELLED ANIMAL BODY 39 

structural units, the cells, of which so many are included 
in the body of any one of the complex animals. 

Protoplasm. — The protoplasm, which is the essential 
substance of the typical animal cell and hence of the 
whole animal body, is a substance of very complex 
chemical and physical make-up. No chemist has yet 
been able to determine its exact chemical constitution, 
and the microscope has so far been unable to reveal 
certainly its physical characters. The most important 
thing known about the chemical constitution of proto- 
plasm is that there are always present in it certain com- 
plex albuminous substances which are never found in 
inorganic bodies. And it is certain that it is on the 
presence of these substances that the power possessed 
by protoplasm of performing the fundamental life-pro- 
cesses depends. Protoplasm is the primitive physical 
basis of life, but it is the presence of the complex albu- 
minous substances in it that makes it so. 

The physical constitution of protoplasm seems to be 
that of a viscous liquid containing many fine globules of a 
liquid of different density and numerous larger globules 
of a liquid of still other density. Some naturalists believe 
the fine globules to be solid grains, while still others 
believe that numerous fine threads of dense protoplasm 
lie coiled and tangled in the clearer, viscous protoplasm. 
But the little we know of the physical structure of proto- 
plasm throws almost no light on the remarkable properties 
of this fundamental life-substance. 



CHAPTER VIII 

CELLULAR STRUCTURE OF THE TOAD (OR 

FROG) 

LABORATORY EXERCISE 

The blood. — Technical Note. — The blood of a frog can be 
studied as it flows through the small vessels in the membranes 
between the toes while the animal is alive. Place a frog on a small 
flat board which has had a hole cut near one end, and with a 
piece of cloth bind it to the board. Spread the web between two 
toes over the hole in the board and keep it in place with pins. 
This done, examine the distended web under the compound micro- 
scope first with low then with higher power, and observe the blood- 
vessels and the blood circulating in them. For a further study of 
the blood kill a toad or frog and place a drop of the blood on a 
slide with a cover-glass over it. 

Put the prepared slide under the microscope and note 
that the blood, which as seen with the unaided eye 
appears to be a red fluid, is made up of a great many 
yellowish elliptical disks or cells, the blood-corpuscles, 
floating in a liquid, the blood-plasma. Here and there 
you may notice amoeboid blood-corpuscles. These are 
irregular-shaped cells which move about by thrusting out 
pseudopodia. They look like some of the unicellular 
animals, as the Amoeba. Can you distinguish a nucleus 
and cell-wall in the blood-cells ? 

Make drawings of these blood-cells. 

The skin. — Technical Note. — Keep a live toad or frog in 
water for some time and note if its skin becomes loose or begins to 
slip away. If the outer skin, epidermis, comes off, take some of the 
shed skin and wash it in water, then stain for three or four minutes 
in a solution of methyl-green and acetic acid (seep. 451). Cut 

40 



CELLULAR STRUCTURE OF THE TOAD (OR FROG) 41 

the pieces of stained skin into small bits and examine one of these 
under the microscope. 

With the low power of the microscope you will note 
that the skin is made up of a great many flat cells placed 
edge to edge. Each one has its cell-wall and a central 
darkly stained nucleus. 

Make a drawing of a portion of the toad's skin. 

The liver. — Technical Note. — Cut through the fresh liver 
of a toad, and with a knife-blade scrape from the cut surface some 
of the liver-cells and place them on a slide with cover-glass. 

Examine under the microscope and observe many 
polygonal cells. Place some of the methyl-green acetic 
stain under the cover-glass and note, after the cells are 
stained, that they have definite boundaries and a central 
nucleus. 

Draw some of these scattered liver-cells. 

The muscles. — Technical Note. — Take a piece of intestine 
from a freshly killed toad, wash it thoroughly and place it in a con- 
centrated solution of salicylic acid in yo% alcohol for 24 hours, 
then gradually heat until about the boiling-point, when the muscles 
will fall to pieces. Transfer the preparation to a watch-crystal and 
tease small bits of isolated muscle with dissecting-needles. Place 
some of the teased muscle-fibres on a slide, cover with cover-glass, 
and add a drop of the methyl-green acetic acid. 

Note the small spindle-shaped muscle-fibres. Each 
one of these fibres is a cell possessing all of the structures 
common to cells, namely, cell-wall, nucleus, etc. 

Make a drawing of a few isolated fibres of muscle. 

From this study of some of the tissues in a toad it will 
be noted that in the first case we had in the blood 
separate cells which moved about freely in the plasma. 
In the second case, that of the epidermis, the cells are 
fixed edge to edge, thus forming a thin tissue; while in 
the third and fourth cases, that of the liver and muscle, 
the cells are not only placed edge to edge, but aggregated 



4 2 ELEMENTARY ZOOLOGY 

into vast masses or bundles, in one case to form the liver 
and in the other case a muscle. The entire body of the 
toad is built up of a colony of simple units (cells) com- 
bined in various forms to make all the various tissues and 
organs. 



CHAPTER IX 

THE MANY-CELLED ANIMAL BODY. —DIF- 
FERENTIATION OF THE CELL 

The many-celled animal body. — In the study of cer- 
tain of the tissues and organs of the toad we have learned 
that the body of this animal is composed of many cells, 
thousands and thousands of these microscopic structural 
units being combined to form the whole toad. This 
many-celled or multicellular condition of the body is true 
of all the animals except the simplest, the unicellular 
Protozoa. Corals, starfishes, worms, clams, crabs, in- 
sects, fishes, frogs, reptiles, birds, and mammals, all the 
various kinds of animals in which the body is composed 
of organs and tissues, agree in the multicellular character 
of the body, and may be grouped together and called the 
many-celled animals in contrast to the one-celled animals. 
This division is one which is recognized by many syste- 
matic zoologists as being more truly primary or funda- 
mental than the division of animals into Vertebrates and 
Invertebrates. The one-celled animals are called Pro- 
tozoa, and the many-celled animals Metazoa. 

Differentiation of the cell. — It is apparent at first 
glance that the cells which compose the body of a many- 
celled animal are not like the simple primitive cell which 
makes up the body of the Amoeba, nor are they like the 
more complexly arranged cell of the Paramoecium. Nor 
are they all like each other. The cells in the toad's blood 
are of two kinds, the white blood-cells, which are very like 

43 



44 ELEMENTARY ZOOLOGY 

the body of Amoeba, and the elliptical disk-like red blood- 
cells. The cells composing the muscles are, moreover, 
like neither kind of blood-cells, and the cells of which the 
liver is composed are not like the cells of the muscles. 
That is, there are many different kinds of cells in the body 
of a many-celled animal. While the single cell which 
composes the whole body of the Amoeba is able to do all 
the things necessary to maintain life, the various cells in the 
body of a complex animal are differentiated or specialized, 
certain cells devoting themselves to a certain function or 
special work, and others to other special functions. For 
example, the cells which compose the organs of the 
nervous system, the brain, ganglia, and nerves, devote 
themselves almost exclusively to the function of sen- 
sation, and they are especially modified for this purpose. 
The highly specialized nerve-cells resemble very little the 
primitive generalized body-cell of Amoeba. The muscle- 
cells of the complex animal body have developed to a 
high degree that power of contraction which is possessed, 
though in but slight degree, by Amoeba. These muscle- 
cells have for their special function this one of contraction, 
and massed together in great numbers they form the 
strongly contractile muscular tissue and muscles of the 
body on which the animal's power of motion depends. 
The cells which line certain parts of the alimentary canal 
are the ones on which the function of digestion chiefly 
rests. And so we might continue our survey of the 
whole complex body. The point of it all is that the 
thousands of cells which compose the many-celled animal 
body are differentiated and specialized; that is, have 
become changed or modified from the generalized primitive 
amoeboid condition, so that each kind of cell is devoted 
to some special work or function and has a special struc- 
tural character fitting it for its special function. In the 
Protozoan body the single cell can perform and does per- 



DIFFERENTIATION OF THE CELL 45 

form all the functions or processes necessary to the life of 
the animal. In the Metazoan body each cell performs, in 
co-operation with many other similar cells, some one 
special function or process. The total work of all the 
cells is the living of the animal. 



CHAPTER X 
HYDRA 

LABORATORY EXERCISE 

Technical Note. — Hydra lives in fresh water, attached to stones, 
sticks, or decayed leaves. It can be found in most open fresh-water 
ponds not too stagnant, often attached to Chara. There are two 
species occurring commonly, H. viridis, the green Hydra, and H 
fuscus, the brown or flesh-colored Hydra. Both are very small 
forms and have to be looked for carefully. Specimens should be 
brought to the laboratory, put into a large dish of water and left 
in the light. Hydra is best studied alive. Place a living specimen 
attached to a bit of weed in a watch-crystal filled with water or on 
a slide with plenty of water and examine with the low power of the 
microscope. 

Note the cylindrical body (fig. 7, A, B) with its flat 
basal attachment and radial tentacles (varying in number) 
which crown the upper end and surround the centrally 
located mouth. Note the movements of Hydra, its powers 
of contraction, and method of taking in food. 

Technical Note. — To feed Hydra, place very small " water- 
fleas" {Daphnia sp.) in the water with it. 

Observe the method by which " water-fleas " are taken 
into the mouth. Food is caught on stinging cells (to be 
studied later) and conveyed to the mouth by the tenta- 
cles. Note that the cylindrical body encloses a cavity, 
the digestive cavity. How is this connected with the ex- 
terior ? If Hydra captures prey too large or is no longer 

hungry, the prey is released, 

46 



HYDRA 



47 



J ^-" v ~^' ^^ 



.nth /} / y 

r 



-y 



y'^\ 



**&-? 






lft;^r^' 






b,trh> 



c 



*=S^T m-.iixltiX-uzt 



trigger hair 

Ued whip 



- 1 







A>^ 



ulial tube" 




Fig. 7 — A, Hydra fusca, with expanded body and a budding individual; 
B, H. fusca, contracted; C, H. fusca, part of outer surface of a tenta- 
cle, greatly magnified. (A and B drawn from live specimens. C. from a 
preparation ) D. Grantia sp. (a sponge), three individuals; E. Grantia 
sp., longitudinal section ; F, Grantia sp., spicules. (D, E, and F 
drawn from preserved specimens.) 



48 ELEMENTARY ZOOLOGY 

Technical Note. — Place small slips of paper on the slide near 
the Hydra, put cover-glass over the whole, and examine with the 
low power of the microscope. 

Note that the whole animal is made up of cells closely 
joined. Are the cells in the tentacles all alike ? Note 
nodule-like projections above some of the cells; these are 
stinging cells, or cnidoblasts. In some cases a small hair- 
like process, the trigger hair or cnidocil, may be seen pro- 
jecting above the surface of the cell. Note in some of the 
tentacles dark-colored particles. These are food-particles 
which have been taken through the mouth into the diges- 
tive cavity and have passed thence into the tentacles. 
The central digestive cavity communicates freely with the 
cavities in the tentacles, for the tentacles are merely 
evaginations of the body-wall. 

Make drawings of the Hydra expanded and of the same 
individual contracted. 

Technical Note. — From the preparation which you have under 
the microscope pull out the slips of paper, thus letting the cover- 
glass drop down on the specimen. With a small pipette put a 
drop of anilin-acetic stain (see p. 451 ) on the slide at one side 
of the cover-glass and with a piece of filter-paper draw the water 
through from the other side of the cover-glass. When the stain is 
diffused press down the cover-glass gently, and examine the tentacles 
first under a low power of the microscope, then under a high one. 

Note the distortion that the animal has undergone 
through the action of the reagent. Observe the cnido- 
blasts of the tentacles and note that many of them have 
thrown out long whip-like processes (fig. 7, C). On 
what parts of the body do the cnidoblasts occur ? Care- 
fully examine one of the cnidoblasts which has been dis- 
charged and note a clear transparent bag-like structure 
within, the nematocyst, to which is attached the long 
whip-like process. In another cnidoblast cell which has 
not been discharged note that the whip-like process is 
coiled about inside of the bag-like structure. The whole 



HYDRA 



49 



apparatus is like the inturned finger of a glove which can 
be blown out by pressure from the inside. The mechan- 
ism is simple. The cnidocil or trigger-hair is touched by 
some animal, an impulse is conveyed to the delicate fibres 
interspersed among the cells (nerve-cells) which stimulate 
the cnidoblast cell, whereupon there is a contraction of 
the contents and, the cnidoblast being compressed, the 
inverted whip-like process turns wrong side out and im- 
pales the animal on its points or barbs. 

Technical Note. — The teacher should be provided with micro- 
scopical sections, both transverse and longitudinal, of the Hydra 
stained in some good general stain (haematoxylin or borax carmine). 
If the teacher has no means of making such preparations, they may 
be procured from dispensers of microscopical supplies. 

From the cross-section of the Hydra make out the 
general structure of the body. Note that it is a hollow 
cylinder consisting of two well-defined layers of cells, an 
outside ectoderm layer and an inner endoderm layer. 
Between these two is yet another thin non-cellular layer 
called the mesoglcea. 

Thus it will be seen that Hydra is made up of two 
layers of cells, the outer ectoderm or skin, which is 
specialized to perform the office of capturing prey as well 
as that of protection, and the inner endoderm, wheh sur- 
rounds the digestive cavity and performs the function of 
digestion. The endoderm lines the body-cavity, particles 
taken in as food being digested by certain digestive cells 
which thrust out amoeboid processes and ingest particles 
of food. Other cells in the endoderm have long flagellate 
processes which vibrate back and forth in the digestive 
cavity, thereby creating currents in the water containing 
food-particles. 

Note, in a cross-section, that there are small ovoid or 
cuboid cells at the bases of the large ectoderm cells. 
These are the interstitial cells. Some of the interstitial 



50 ELEMENTARY ZOOLOGY 

cells become modified and pushed up between the ecto- 
derm cells to form cnidoblast cells. Many of the 
endoderm as well as ectoderm cells have muscle-processes 
which spread out from the base of the cell and which 
serve to contract and expand the body. 

Technical Note. — In the specimens which have been collected 
perhaps two methods of reproduction will be observed. Place 
healthy Hydrce in a wide-mouthed jar in the sunlight with plenty 
of water and food. In a few days active budding will take place. 

Observe the method of reproduction in Hydra. Com- 
monly the parent produces small buds, which at first are 
only evaginations of the body-wall, but which later 
develop tentacles and a mouth of their own. Subse- 
quently the bud becomes constricted at the base, separates 
from the parent, and the young Hydra begins a distinct 
existence. 

Another mode of reproduction takes place which, in 
distinction from the asexual method just mentioned, is 
called sexual reproduction. This last is the method 
common to most of the higher organisms. You may note 
that in some Hydrce there is a swelling or bulging of the 
ectoderm of the body-wall in the region just below the 
tentacles. These are the sperm-glands. Within these are 
produced sperm-cells which break away in great clusters 
to fertilize the ova, or eggs, Note a larger bulging of the 
body-w r all nearer the lower end of the body which, under 
high power, has a granular appearance. This is the egg- 
gland, in which develops a single ovum or egg. The 
ovum breaks from its covering and is fertilized by sperm- 
cells from another individual. In forms like Hydra, 
where both sexes are represented in a single individual, 
the organism is termed manceciotis or Jicrmaphroditic. In 
connection with reproduction Chapter XIII should be 
studied. 



HYDRA 51 

An instructive experiment can be performed by cutting 
a Hydra into two or more parts, when (usually) each of 
the various parts will develop into a complete Hydrce. 
This process may be called reproduction by fission, but it 
rarely occurs naturally, 



CHAPTER Xt 
THE SIMPLEST MANY-CELLED ANIMALS 

Cell differentiation and body organization in Hydra. 

— From the examination of Hydra we have learned that 
there are true many-celled animals which are much less 
complex in structure than the toad and crayfish. The 
body of Hydra, like the body of the toad, is composed of 
many cells, but these cells are of only a few different 
kinds; that is, show but little differentiation. There is 
relatively little division of the body into distinct organs. 
Still, certain parts of the body devote themselves princi- 
pally to certain particular functions. Thus all the food is 
taken in through the single " mouth-opening ' at the 
apical free end of the cylindrical body, and there are 
certain organs, the tentacles, whose special business or 
function it is to find and seize food and to convey it to the 
mouth. After the food is taken into the cylindrical body- 
cavity it is digested by special cells which line the cavity. 
Some of these cells are unusually large, and each contains 
one or more contractile vacuoles. From the free ends of 
these cells, the ends which are next to the body-cavity, 
project pseudopods or flagella. These protoplasmic 
processes are constantly changing their form and number. 
In addition to these large sub-amoeboid cells there are, in 
this inner layer of cells lining the body-cavity, and 
especially abundant near the base or bottom of the cavity, 
many long, narrow, granular cells. These are gland- 
cells which secrete a digestive fluid. The food captured 
by the tentacles and taken in through the mouth-opening 
disintegrates in the body-cavity, or digestive cavity as it 

52 



THE SIMPLEST MANY-CELLED ANIMALS 53 

may be called. The digestive fluid secreted by the 
gland-cells acts upon it so that it becomes broken into 
small parts. These particles are seized by the projecting 
pseudopods of the sub-amoeboid cells and taken into the 
body-protoplasm of these cells. The cells of the outer 
layer of the body do not take food directly, but receive 
nourishment only by means of and through the cells of 
the inner layer. The body-cavity of Hydra is a very 
simple special organ of digestion. 

In the outer layer of cells there are some specially 
large cells whose inner ends are extended as narrow 
pointed prolongations directed at right angles with the 
rest of the cell. These processes are very contractile and 
are called muscle-processes. Each one is simply a 
specially contractile continuation of the protoplasm of the 
cell-body. There are also in this layer some small cells 
very irregular in shape and provided with unusually large 
nuclei. These cells are more irritable or sensitive than 
the others and are called nerve-cells. We have thus in 
Hydra the beginnings of muscular organs and of nerve- 
organs. But how simple and unformed compared with 
the muscular and nervous systems of the toad and crayfish ! 
There is no circulatory system, nor are there any special 
organs of respiration. 

But Hydra is far in advance of Amoeba or Paramecium. 
Its body is composed of thousands of distinct cells. Some 
of these cells devote themselves especially to food-taking, 
some especially to the digestion of food ; some are 
specially contractile, and on them the movements of the 
body depend, while others are specially irritable or sensi- 
tive, and on them the body depends for knowledge of the 
contact of prey or enemies. In the cnidobla^t cells, those 
with the stinging threads, there is a very wide departure 
from the simple primitive type of cells. There is in 
Hydra a manifest differentiation of the cells into various 



54 ELEMENTARY ZOOLOGY 

kinds of cells. The beginnings of distinct tissues and 
organs are indicated. 

Degrees in cell differentiation and body organization. 

— In the study of the cellular constitution of the tissues 
and organs of the toad, we found to what a high degree 
the differentiation of the cells may attain, and in the study 
of the anatomy of the toad w r e found how thoroughly these 
differentiated cells may be combined and organized into 
body-parts or organs. The body of the toad is made up 
of distinct organs, each composed of highly differentiated 
or specialized cells. The body of Hydra is composed of 
cells for the most part only slightly differentiated and 
hardly recognizably grouped or combined into organs. 
These two conditions are the extremes in the body- 
structure of the many-celled animals. Between them 
is a host of intermediate conditions of cell differentia- 
tion and body organization. When we come to the 
study of other members of the great branch of simple 
many-celled animals to which Hydra belongs (see 
Chapter XVII), it will be found that some of them 
show a slight advance in complexity beyond Hydra. 
Higher in the scale of animal life the forms will be found 
still more and more complex, with ever-increasing differ- 
entiation of the cells, with the combination of the differ- 
entiated cells into distinct organs, and the co-ordination 
of organs into systems of organs up to the extreme shown 
by the birds and mammals. And hand in hand with this 
increasing complexity of structure goes ever-increasing 
complexity or specialization of function. Breathing is a 
simple function or process with Hydra, w T here each body- 
cell takes up oxygen for itself, but it is a complex business 
with the toad, or with a bird or mammal, where certain 
complex structures, the lungs and accessory parts, and 
the heart, blood-vessels and blood all work together to 
distribute oxygen to all parts of the body. 



CHAPTER XII 
DEVELOPMENT OF THE TOAD 

FIELD AND LABORATORY EXERCISE 

Technical Note. — As the work of this chapter, or some similar 
work in getting acquainted with the postembryonic development 
of a many-celled animal, should be done early in the course, and 
as most schools open in the fall, it will perhaps be impossible to 
make this first study of development from live specimens in the field. 
In such case the examination of a series of prepared specimens, 
previously obtained by the teacher, must be resorted to. In the 
spring the development of several kinds of animals, including the 
toad, can be studied from live specimens in the field or in breeding- 
cages and aquaria in the laboratory. The eggs of the toad may be 
found in April and May (the toads are heard trilling at egg-laying 
time) in ponds. The eggs look like the heads of black pins, and are 
in single rows in long strings of transparent jelly, which are usually 
wound around sticks or plant-stems at the bottom of the pond near 
the shore. Bring some of these strings into the schoolroom and 
keep them in water in shallow dishes. Keep them in the light, but 
not in direct sunlight. In the dishes put some small stones and 
mud from the pond, arranging them in a slope, thus making different 
depths of water. Stones with green algas on should be selected, for 
algas are the food of the tadpoles. The eggs will hatch in two or 
three days, and if too many tadpoles are not kept in the dish, and 
the little aquarium be well cared for, the whole postembryonic de- 
velopment of the toad can be well observed. For the study of the 
development from prepared specimens the teacher should have a 
complete series of stages from egg to adult toad in alcohol. The 
specimens may be examined by the students in connection with a 
talk from the teacher on the life-history of the toad. 

If the study is made from prepared specimens, make 
drawings of egg-strings, and of a single egg magnified 
and shaded to indicate its color. Draw each specimen of 
the series of tadpoles, noting in the youngest the presence 
of gills and tail and absence of legs and eyes; in the 

55 



56 ELEMENTARY ZOOLOGY 

older the appearance of eyes, the shrivelling of the gills, 
shrinking of the tail and development of legs ; in the still 
older the characteristic shape, in miniature, of the adult 
toad. 

In observing the course of development of the living 
specimens there should be made, in addition to the draw- 
ings, notes showing the duration of the egg stage, and 
the time elapsing between all important changes (as seen 
externally) in the body of the young. Observations and 
notes on the general behavior of tadpoles should also be 
made ; note the swimming, the feeding, the gradual leav- 
ing of the water, etc. 

In addition to the easily seen external changes in the 
body, very important ones in the internal organs take 
place during development. Perhaps the most important 
of these concerns the lungs. The young gilled toad 
breathes as a fish does, but gradually its gills are lost, 
while at the same time lungs develop and the tadpole 
comes to the surface to breathe air like any lunged aquatic 
animal. The toad on leaving the water changes its diet 
from vegetable to animal food ; a tadpole feeds on aquatic 
algae; a toad preys on insects. Correlated with the 
change in habit, the intestine during development under- 
goes some marked changes, becoming relatively dimin- 
ished in length. 

For an account of the development of the toad see 
Gage's "Life-history of a Toad' or Hodge's "The 
Common Toad. " 



CHAPTER XIII 

MULTIPLICATION AND DEVELOPMENT.— MUL- 
TIPLICATION OF ONE-CELLED ANIMALS 

Multiplication. — We know that any living animal has 
parents; that is, has been produced by other animals 
which may still be living or be now dead or, as with 
Amccba, may have changed, by division, into new indi- 
viduals. Individuals die, but before death, they produce 
other individuals like themselves. If they did not, their 
kind or species would die with them. This production 
of new animals constantly going on is called the repro- 
duction or multiplication of animals. The process is 
well called multiplication, because each female animal 
normally produces more than one new individual. She 
may produce only one at a time, one a year, as many of 
the sea-birds do or as the elephant does, but she lives 
many years. Or she may produce hundreds, or thou- 
sands, or even millions of young in a very short time. 
A lobster lays 10,000 eggs at a time. Nearly nine 
millions of eggs have been taken from the body of a 
thirty-pound female codfish. As a matter of fact but 
very, very few of these eggs produce new animals which 
reach maturity. From the 10,000 eggs produced by the 
lobster each year an average of but two new mature 
lobsters is produced. There is always a struggle for food 
and for place going on among animals, for many more 
are produced than there are food and room for, and so of 
all the new or young animals which are born the great 

57 



5 8 ELEMENTARY ZOOLOGY 

majority are killed before they reach maturity. In a later 
chapter more attention will be given to this great struggle 
for life. 

In the preceding paragraph it has been stated that 
" we know that any living animal has parents ; that is, has 
been produced by other animals which may still be living 
or be now dead.' This is a statement, however, which 
has found complete acceptance only in modern times. 
It is a familiar fact that a new kitten comes into the world 
only through being born ; that it is the offspring of parents 
of its kind. But we may not be personally familiar with 
the fact that a new starfish comes into the world only as 
the production of parent starfish, or that a new earth- 
worm can be produced only by other earthworms. But 
naturalists have proved these statements. . All life comes 
from life; all organisms are produced by other organisms. 
And new individuals are produced by other individuals of 
the same kind. That these statements are true all 
modern observations and investigations of the origin of 
new individuals prove. But in the days of the earlier 
naturalists the life of the microscopic organisms like 
Amoeba and Paramoecium, and even that of many of the 
larger but unfamiliar animals, was shrouded in mystery. 
And various and strange beliefs were held regarding the 
origin of new individuals. 

Spontaneous generation. — The ancients believed that 
many animals were spontaneously generated. The early 
naturalists thought that flies arose by spontaneous genera- 
tion from the decaying matter of dead animals. Frogs 
and many insects were thought to be generated spontane- 
ously from mud, and horse-hairs in water were thought 
to change into water-snakes. But such beliefs were 
easily shown to be based on error, and have been long 
discarded by zoologists. But the belief that the micro- 
scopic organisms, such as bacteria and infusoria, were 



MULTIPLICATION AND DEVELOPMENT 59 

spontaneously generated in stagnant water or decaying 
organic liquids was held by some naturalists until very 
recent times. And it was not so easy to disprove the 
assertions of such believers. If some water in which 
there are apparently no living organisms, however 
minute, be allowed to stand for a few days, it will 
come to swarm with microscopic plants and animals. 
Any organic liquid, as a broth or a vegetable infusion, 
exposed to the air for a short time becomes foul through 
the presence of innumerable microscopic organisms. But 
it has been certainly proved that these organisms are not 
spontaneously produced in the water or organic fluid. 
A few of them enter the water from the air, in which there 
are always greater or less numbers of spores of micro- 
scopic organisms. These spores germinate quickly when 
they fall into water or some organic liquid, and the rapid 
succession of generations soon gives rise to the hosts of 
bacteria and one-celled animals which infest all standing 
water. If all the active organisms and inactive spores in 
a glass of water are killed by boiling the water, and this 
sterilized water be put into a sterilized glass, and this 
glass be so well closed that germs or spores cannot pass 
from the air without into the sterilized liquid, no living 
animals will ever appear in it. We know of no instance 
of the spontaneous generation of animals, and all the 
animals whose life-history we know are produced by other 
animals of the same kind. 

Simplest multiplication and development. — The sim- 
plest method of multiplication and the simplest kind of 
development shown among animals are exhibited by such 
simple animals as Amoeba and Paramcecium. The pro- 
duction of new individuals is accomplished in Amoeba by 
a simple division or fission of its body (a single cell) into 
two practically equivalent parts. An Amoeba which has 
grown for some time contracts all of its finger-like 



6o ELEMENTARY ZOOLOGY 

processes, the pseudopodia, and its body becomes con- 
stricted. This constriction or fissure increases inwards 
so that the body is soon divided fairly in two. There are 
now two Amcebce, each half the size of the original one; 
each, indeed, actually one-half of the original one. The 
original Amoeba was the parent; the two halves of it are 
the young. Each of the young possesses all of the char- 
acteristics and powers of the parent; each can move, eat, 
feel, grow, and reproduce by fission. The only change 
necessary for the young or new Amoeba to become like its 
parent, is that of simple growth to a size about twice its 
present size. The development here is reduced to a 
minimum. Just as the simplest animals perform the other 
life-processes, such as taking and digesting food, breath- 
ing and feeling, in an extremely primitive simple way, so 
do they perform the necessary life-process of reproduction 
or multiplication in the simplest w r ay shown among 
animals. 

In the case of Paramoecium the process of multiplication 
is slightly more complex than that of Amoeba in the fact 
that sometimes before the simple fission of the body takes 
place the interesting phenomenon of conjugation occurs. 
Paramoecium may reproduce itself for many generations 
by simple fission, but a generation finally appears in which 
conjugation takes place. Two individuals come together 
and each exchanges with the other a part of its nucleus. 
Then the two individuals separate and each divides into 
two. The result of the conjugation, or the coming 
together, of two individuals with mutual interchange of 
nuclear substance is to give to the new Paramoecia pro- 
duced by the conjugating individuals a body which 
contains part of the body-substance of two distinct indi- 
viduals. If the two conjugating individuals differ at all — 
and they always do differ, because no two individual 
animals, although belonging to the same species, are 



MULTIPLICATION AND DEVELOPMENT 61 

exactly alike — the new individual, made up of parts of 
each of them, will differ slightly from both. Nature 
seems intent on making every new individual differ slightly 
from the individual which precedes it. And the method 
of multiplication which Nature has adopted to produce 
the result is the method which we have seen exhibited in 
its simplest form in the case of Paramcvcium — the method 
of having two individuals take part in the production of 
a new one. 

The development of the new Par amcecia is a little more 
complex than that oi Amoeba. Not only must the new 
Paramecium grow to the size of the original one, but it 
must develop those slight, but apparent, modifications of 
the parts of its body which we can recognize in the full- 
grown, fully developed Paramecium individual. A new 
mouth-opening must develop on the new individual 
formed of the hinder half of the original Paramcvcium and 
new cilia must be developed. Thus there is a slight 
advance in complexity of development, just as there is in 
complexity of structure in Paramecium as compared with 
Amccba. In the many-celled animals this complexity of 
development is carried to an extreme. 

Birth and hatching. — When a young animal is born 
alive, it usually resembles in appearance and structure the 
parent, although of course it is much smaller, and requires 
always a certain time to complete its development and 
become mature. A young kangaroo or opossum is 
carried for some time after its birth in an external pouch 
on the mother's body and is a very helpless animal. A 
young kitten is born with eyes not yet opened and must 
be fed by the mother for several weeks. On the other 
hand young Rocky Mountain sheep are able to run about 
swiftly within a few hours after birth. 



62 ELEMENTARY ZOOLOGY 

Most animals appear first as eggs laid by the mother. 
This is true of the birds, the reptiles, the fishes, the 
insects, and most of the hosts of invertebrate animals, 
This egg may be cared for by the parent as with the 
birds, or simply deposited in a safe place as with most 
insects, or perhaps dropped without care into the water as 
with most marine invertebrates. The young animal which 
issues from the egg may at the time of its hatching 
resemble the parent in appearance and structural character 
(although always much smaller) as with the birds, some 
of the insects, and many of the other animals. Or it may 
issue in a so-called larval condition, in which it resembles 
the parent but slightly or not at all, as is the case with 
the gill-bearing, legless, tailed tadpole of the frog or the 
crawling, wingless, wormlike caterpillar of the butterfly, 
or the maggot of the house-fly. 

Life-history. — Any animal which hatches from an egg 
has undergone a longer or shorter period of development 
within the egg-shell before hatching. The development 
of an animal from first germ-cell to the time it leaves the 
egg, for example, the development of the embryo chick 
from the first cell to time of hatching, is called its em- 
bryonic development; and the development from then on, 
for example, that of the chick to adult hen or rooster, 
or that of tadpole to frog, is called the post-embryonic 
development. Beginning students of animals cannot 
study the embryonic development {embryology) of animals 
readily, but they can in many cases easily follow the 
course of the post-embryonic development, and this study 
will always be interesting and valuable. When the 
" life-history " of an animal is spoken of in this book, or 
other elementary text-book of zoology, it is the history 
of the life of the animal from the time of its birth or 
hatching to and through adult condition that is meant, 
not the complete life-history from beginning single egg- 



MULTIPLICATION AND DEVELOPMENT 63 

cell to the end. In all of the study of the different kinds 
of animals to which the rest of this book is devoted, 
attention will be paid to their life-history. 



PART II 

SYSTEMATIC ZOOLOGY 

CHAPTER XIV 
THE CLASSIFICATION OF ANIMALS 

Basis and significance of classification. — It is the 

common knowledge of all of us that animals are classified: 
that is, that the different kinds are arranged in the mind 
of the zoologist and in the books of natural history, in 
various groups, and that these various groups are of 
different rank or degree of comprehensiveness. A group 
of high rank or great comprehensiveness includes groups 
of lower rank, and each of these includes groups of still 
lower rank, and so on, for several degrees. For example, 
we have already learned that the toad belongs to the 
great group of back-boned animals, the Vertebrates, as 
the group is called. So do the fishes and the birds, the 
reptiles and the mammals or quadrupeds. But each of 
these constitutes a lesser group, and each may in turn be 
subdivided into still lesser groups. 

In the early days of the study of animals and plants 
their classification or division into groups was based on 
the resemblances and the differences which the early 
naturalists found among the organisms they knew. At 
first all of the classifying was done by paying attention 
to external resemblances and differences, but later when 
naturalists began to dissect animals and to get acquainted 

65 



66 ELEMENTARY ZOOLOGY 

with the structure of the whole body, the differences and 
likenesses of inner parts, such as the skeleton and the 
organs of circulation and respiration, were taken into ac- 
count. At the present time and ever since the theory of 
descent began to be accepted by naturalists (and there is 
practically no one who does not now accept it), the classifi- 
cation of animals, while still largely based on resemblances 
and differences among them, tells more than the simple 
fact that animals of the same group resemble each other 
in certain structural characters. It means that the mem- 
bers of a group are related to each other by descent, that 
is, genealogically. They are all the descendants of a 
common ancestor ; they are all sprung from a common 
stock. And this added meaning of classification explains 
the older meaning; it explains why the animals are alike. 
The members of a group resemble each other in structure 
because they are actually blood relations. But as their 
common ancestor lived ages ago, we can learn the history 
of this descent, and find out these blood relationships 
among animals only by the study of forms existing now, 
or through the fragmentary remains of extinct animals 
preserved in the rocks as fossils. As a matter of fact 
we usually learn of the existence of this actual blood- 
relationship, or the fact of common ancestry among 
animals, by studying their structure and finding out the 
resemblances and differences among them. If much alike 
we believe them closely related; if less alike we believe 
them less closely related, and so on. So after all, thougli 
the present-day classification means something more, 
means a great deal more, in fact, than the classification 
of the earlier naturalists means, it is largely based on 
and determined by resemblances and differences just as 
was the old classification. Sometimes the fossil remains 
of ancient animals tell us much about the ancestry and 
descent of existing forms. For example, the present-day 



THE CLASSIFICATION OF ANIMALS 6y 

one-toed horse has been clearly shown by series of fossils 
to be descended from a small five-toed horse-like animal 
which lived in the Tertiary age. 

Importance of development in determining classifica- 
tion. — A very important means of determining the 
relationships among animals is by studying their develop- 
ment. If two kinds of animals undergo very similar 
development, that is, if in their development and growth 
from egg-cell to adult they pass through similar stages, 
they are nearly related. And by the correspondence or 
lack of correspondence, by the similarity or dissimilarity 
of the course of development of different animals much 
regarding their relationship to each other is revealed. 
Sometimes two kinds of animals which are really nearly 
related come to differ very much in appearance in their 
fully developed adult condition because of the widely differ- 
ent life-habits the two may have. But if they are nearly 
related their developmental stages will be closely similar 
until the animals are almost fully developed. For exam- 
ple, certain animals belonging to the group w T hich includes 
the crabs, lobsters, and crayfishes, have adopted a para- 
sitic habit of life, and in their adult condition live attached 
to the bodies of certain kinds of true crabs. As these 
parasites have no need of moving about, being carried by 
their hosts, they have lost their legs by degeneration, and 
the body has come to be a mere sac-like pulsating mass, 
attached to the host by slender root-like processes, and 
not resembling at all the bodies of their relatives the 
crabs and crayfishes. If we had to trust, in making out 
our classification, solely to structural resemblances and 
differences, we should never classify the Sacculina (the 
parasite) in the group Crustacea, which is the group in- 
cluding the crabs and lobsters and crayfishes. But the 
young Sacculina is an active free-swimming creature 
resembling the young crabs and young shrimps. By a 



68 ELEMENTARY ZOOLOGY 

study of the development of Sacculina we find that it is 
more closely related to the crabs and crayfishes and the 
other Crustaceans than to any other animals, although in 
adult condition it does not at all, at least in external ap- 
pearance, resemble a crab or lobster. 

Scientific names. — To classify animals then, is to deter- 
mine their true relationships and to express these relation- 
ships by a scheme of groups. To these groups proper 
names are given for convenience in referring to them. 
These proper names are all Latin or Greek, simply 
because these classic languages are taught in the schools 
and colleges of almost all the countries in the world, and 
are thus intelligible to naturalists of all nationalities. In 
the older days, indeed, all the scientific books, the 
descriptions and accounts of animals and plants, were 
written in Latin, and now most of the technical 
words used in naming the parts of animals and 
plants are Latin. So that Latin may be called the 
language of science. For most of the groups of animals 
we have English names as well as Greek or Latin ones 
and when talking with an English-speaking person we 
can use these names. But when scientific men write of 
animals they use the names which have been agreed on 
by naturalists of all nationalities and which are understood 
by all of these naturalists. These Latin and Greek 
names of animals laughed at by non-scientific persons as 
"jaw-breakers," are really a great convenience, and save 
much circumlocution and misunderstanding. 

AN EXAMPLE OF CLASSIFICATION." 

TECHNICAL Note. — There should be provided a small set of bird- 
skins which will serve just as well as freshly killed birds, and which 
may be used for successive classes, thus doing away with the neces- 
sity ol shooting birds. The birds suggested for use are among the 
commonest and most easily recognizable and obtainable. They may 
be found in any locality at any time of the year. The skins can 



THE CLASSIFICATION OF ANIMALS 69 

be made by some boy interested in birds and acquainted with 
making skins, or by the teacher, or can be purchased from a natur- 
alists' supply store, or dealer in bird skins. The skins will cost 
about 25 cents each. This example or lesson in classification can 
be given just as well of course w T ith other species of birds, or with 
a set of some other kinds of animals, if the teacher prefers. Insects 
are especially available, butterflies perhaps offering the most readily 
appreciated resemblances and differences. 

Species. — Examine specimens of two male downy 
woodpeckers (the males have a scarlet band on the back 
of the head). (In the western States uses Gardiner's 
downy woodpecker.) Note that the two birds are of the 
same size, have the same colors and markings, and are 
in all respects alike. They are of the same kind; simply 
two individuals of the same kind of animal. There are 
hosts of other individuals of this kind of bird, all alike. 
This one kind of animal is called a species. The species 
is the smallest * group recognized among animals. No at- 
tempt is made to distinguish among the different individuals 
of one kind or species of animal as we do in our own case. 

Examine a specimen of the female downy wood- 
pecker. It is like the male except that it does not have 
the scarlet neck-band. But despite this difference we 
know that it belongs to the same species as the male 
downy because they mate together and produce young 
woodpeckers, male and female, like themselves. There 
are thus two sorts of individuals, t male and female, com- 
prised in each species of animal. A species is a group of 
animals comprising similar individuals which produce 
new individuals of the same kind usually after the mating 
together of individuals of two sexes which may differ 
somewhat in appearance and structure. 

* The lesser group called variety, or subspecies, we may leave out of 
consideration for the present. 

\ Some species of animals are not represented by male individuals ; and 
in some all the individuals are hermaphrodites, as explained in chapter 
XIV. 



70 ELEMENTARY ZOOLOGY 

Examine a male hairy woodpecker and a female ; (in 
western States substitute a Harris's hairy woodpecker). 
Note the similarity in markings and structure to the 
downy. Note the marked difference in size, Make notes 
of measurements, colors and markings, and drawings of 
bill and feet, showing the resemblances and the differ- 
ences between the downy woodpecker and the hairy 
woodpecker. These two kinds of woodpeckers are very 
much alike, but the hairy woodpeckers are always much 
larger (nearly a half) than the downy woodpeckers and 
the two kinds never mate together. The hairy wood- 
peckers constitute another species of bird. 

Genus. — Examine now a flicker (the yellow-shafted 
or golden-winged flicker in the East, the red-shafted 
flicker in the West). Compare it with the downy wood- 
pecker and the hairy woodpecker. Make notes referring 
to the differences, also the resemblances. The flicker 
is very differently marked and colored and is also much 
larger than the downy woodpecker, but its bill and feet 
and general make-up are similar and it is obviously a 
' ' woodpecker. ' It is, however, evidently another species 
of woodpecker, and a species which differs from either the 
downy or the hairy woodpecker much more than these 
two species differ from each other. There are two other 
species of flickers in North America which, although 
different from the yellow-shafted flicker, yet resemble it 
much more than they do the downy and hairy wood- 
peckers or any other woodpeckers. We can obviously 
make two groups of our woodpeckers so far studied, 
putting the downy and hairy woodpeckers (together with 
half a dozen other species very much like them) into one 
group and the three flickers together into another group. 
Each of these groups is called a germs, and genus is thus 
the name of the next group above the species. A genus 
usually includes several, or if there be such, many, 



THE CLASSIFICATION OF ANIMALS 71 

similar species. Sometimes it includes but a single known 
species. That is, a species may not have any other 
species resembling it sufficiently to group with it, and so 
it constitutes a genus by itself. If later naturalists should 
find other species resembling it they would put these new T 
species into the genus with the solitary species. Each 
genus of animals is given a Greek or Latin name, of a 
single word. Thus the genus including the hairy and 
downy woodpeckers is called Dryobates; and the genus 
including the flickers is called Colaptes. But it is neces- 
sary to distinguish the various species which compose the 
genus Colaptes, and so each species is given a name which 
is composed of two words, first the word which is the 
name of the genus to which it belongs, and, second, a 
word which may be called the species word. The species 
word of the Yellow-shafted Flicker is auratus (the Latin 
word for golden), so that its scientific name is Colaptes 
auratus. The natural question. Why not have a single 
word for the name of each species ? may be answered thus : 
There are already known more than 500,000 distinct 
species of living animals ; it is certain that there are no 
less than several millions of species of living animals ;. 
new species are being found, described and named con- 
stantly; with all the possible ingenuity of the word- 
makers it would be an extremelv difficult task to find or 
to build up enough words to give each of these species a 
separate name. This is not attempted. The same 
species word is often used for several different species of 
animals, but never for more than one species belonging 
to a given genus. And the names of the genera are 
never duplicated. (There are, of course, much fewer 
genera than species, and the difficulty of finding words 
for them is not so serious.) Thus the genus word in the 
two-word name of a species indicates at once to just what 
particular genus in the whole animal kingdom the species 



72 ELEMENTARY ZOOLOGY 

belongs, while the second or species word distinguishes it 
from the few or many other species which are included in the 
same genus. This manner of naming species of animals 
and plants (for plants are given their scientific names 
according to the same plan) was devised by the great 
Swedish naturalist Linnaeus in the middle of the 
eighteenth century and has been in use ever since. 

Family. — Examine a red-headed woodpecker (Mela- 
nerpes erythrocephalus) and a sapsucker (Sphyrapicus 
varins) and any other kinds of woodpeckers which can be 
got. Find out in what ways the hairy and downy 
woodpeckers (genus Dry ob cites), the flickers (genus 
Colaptes) and the other woodpeckers resemble each other. 
Examine especially the bill, feet, wings and tail. These 
birds differ in size, color and markings, but they are 
obviously all alike in certain important structural respects. 
We recognize them all as woodpeckers. We can group 
all the woodpeckers together, including several different 
genera, to form a group which is called a family. A 
family is a group of genera which have a considerable 
number of common structural features. Each family is 
given a proper name consisting of a single word. The 
family of woodpeckers is named Picidce. 

We have already learned that resemblances between 
animals indicate (usually) relationship, and that classify- 
ing animals is simply expressing or indicating these 
relationships. When we group several species together 
to form a genus we indicate that these species are closely 
related. And similarly a family is a group of related 
genera. 

Order. — There are other groups* higher or more com- 

*Each of these higher groups has a proper name composed of a single 
word. In the case of no group except the species is a name-word ever 
duplicated. Each genus, family, order, or higher group has a name- word 
peculiar to it ? and belonging to it alone. 



THE CLASSIFICATION OF ANIMALS 73 

prehensive than families, but the principle on which they 
are constituted is exactly the same as that already 
explained. Thus a number of related families are grouped 
together to form an order. All the fowl-like birds, in- 
cluding the families of pheasants, turkeys, grouse and 
quail, all obviously related, constitute the order of gal- 
linaceous birds called Gallince. The families of vultures, 
hawks and owls constitute the order of birds of prey, 
the Raptor es, and the families of the thrushes, wrens, 
warblers, sparrows, black-birds, and many others con- 
stitute the great order of perching birds (including all the 
singing birds) called the Passeres. 

Class and branch. — But it is evident that all of these 
orders, together with the other bird orders, ought to be 
combined into a great group, which shall include all the 
birds, as distinguished from all other animals, as the 
fishes, insects, etc. Such a group of related orders is 
called a class. The class of birds is named Aves. There 
is a class of fishes, Pisces, and one of frogs and salaman- 
ders, Batrachia, one of snakes and lizards called Reptilia, 
and one of the quadrupeds which give milk to their young 
called Mammalia. Each of these classes is composed of 
several orders, each of which includes several families and 
so on down. But these five classes of Pisces, Batrachia, 
Reptilia, Aves and Mammals agree in being composed of 
animals which have a backbone or a backbone-like struc- 
ture, while there are many other animals which do not 
have a backbone, such as the insects, the starfishes, etc. 
Hence these five backboned classes may be brought 
together into a higher group called a branch or phylum. 
They compose the branch of backboned animals, the 
branch Vertebrata; all the animals like the starfishes, 
sea-urchins and sea-lilies which have the parts of their 
body arranged in a radiate manner compose the branch 
Echinodermata; all the animals like the insects and 



74 ELEMENTARY ZOOLOGY 

spiders and centipedes and crabs and crayfishes which 
have the body composed of a series of segments or rings 
and have legs or appendages each composed of a series 
of joints or segments make up the branch Arthropoda. 
And so might be enumerated all the great branches or 
principal groups into which the animal kingdom is divided. 
In the remainder of this book the classification of 
animals is always kept in sight, and the student will see 
the terms species, genus, family, order, etc., practically 
used. In it all should be kept constantly in mind the 
significance of classification, that is, the existence of actual 
relationships among animals through descent. 



CHAPTER XV 

BRANCH PROTOZOA: THE ONE-CELLED 

ANIMALS 

Of this group the structure and life-history of the 
Amoeba [Amoeba sp.) and the Slipper Animalcule (Para- 
mecium sp.) have already been treated in Chapter VI. 
Another example is the 

BELL ANIMALCULE i Vorticella sp.) 

Technical Note. — Specimens of Vorticella may usually be 
found in the same water with Amceba and Paramcecium. The 
individuals live together in colonies, a single colony appearing to 
the naked eye as a tiny whitish mould-like tuft or spot on the 
surface of some leaf or stem or root in the water. Touch such a 
spot with a needle, and if it is a Yorticellid colony it will contract 
instantly. Bring bits of leaves, stems, etc., bearing Yorticellid 
colonies into the laboratory and keep in a small stagnant-water 
aquarium (a battery-jar of pond-water will do). 

Examine a colony of Vorticella in a watch-glass of 
water or in a drop of water on a glass slide under the 
microscope. Note the stemmed bell-shaped bodies 
which compose the colony. Each bell and stem together 
form an individual Vorticella (fig. 8.) How are the 
members of the colony fastened together ? Tap the slide 
and note the sudden contraction of the animals; also the 
details of contraction in the case of an individual. Watch 
the colony expand ; note the details of this movement in 
the case of an individual. 

Make drawings showing the colony expanded and con- 
tracted. 

With higher power examine a single individual. Note 

75 



7 6 



ELEMENTARY ZOOLOGY 



the thickened, bent-out, upper margin of the bell. This 

margin is called the peristome. With 
what is it fringed ? The free end of the 
bell is nearly filled by a central disk, 
the epistome, with arched upper surface 
and a circlet of cilia. Between the 
epistome and peristome is a groove, 
the mouth or vestibule, which leads 
into the body. Study the internal 
structure of the transparent, bell- 
shaped body. Note the differentia- 
tion of the protoplasm comprising the 
body into an inner transparent color- 
less endosarc containing various dark- 
colored granules, vacuoles, oil-drops, 
etc., and an outer uniformly granular 
ectosarc not containing vacuoles. Is 
the stalk formed of ectosarc or en- 
dosarc or of both ? Note the curved 
nucleus lying in the endosarc. (This 
may be difficult to distinguish in some 
specimens.) Note the numerous large 
circular granules, the food vacuoles. 
Note the contractile vesicle, larger and 
clearer than the food vacuoles. Note 
the thin cuticle lining the whole body 
externally. A high magnification will show fine trans- 
verse ridges or rows of dots on the cuticle. 

Make a drawing showing the internal structure. 
Observe a living specimen carefully for some time to 
determine all of its movements. Note the contraction 
and extension of the stalk, the movements of the cilia of 
peristome and epistome, the flowing or streaming of the 
fluid endosarc (indicated by the movements of the food 
vacuoles), the behavior of the contractile vesicle. 




sp. 



FlG. 8. — Vorticella 
one individual with 
stalk coiled, and one 
with stalk extended. 
(From life:) 



BRANCH PROTOZOA: THE ONE-CELLED ANIMALS 77 

Make notes and drawings explaining these motions. 

Specimens of Vorticella may perhaps be found dividing, 
or two bell-shaped bodies may be found on a single stem, 
one of the bodies being sometimes smaller than the other. 
These two bodies have been produced by the longitudinal 
division or fission of a single body. In this process a 
cleft first appears at the distal end of the bell-shaped 
body, and gradually deepens until the original body is 
divided quite in two. The stalk divides for a very short 
distance. One of the new bell-shaped bodies develops a 
circlet of cilia near the stalked end. After a while it 
breaks away and swims about by means of this basal 
circlet of cilia. Later it settles down, becomes attached 
by its basal end, loses its basal cilia and develops a stalk, 
gugation occurs sometimes, but it is unlike the 
conjugation of Paramccehun in two important points: 
Firstly, the conjugation is between two dissimilar forms ; 
an ordinary large-stalked form, and a much smaller free- 
swimming form which has originated by repeated division 
of a large form. Secondly, the union of the two is a 
complete and permanent fusion, the smaller being 
absorbed into the larger. This permanent fusion of a 
small active cell with a relatively large fixed cell, followed 
by division of the fused mass, presents a striking analogy 
to the process of sexual reproduction occurring in higher 
animals." 

OTHER PROTOZOA 

Besides the Amoeba, Paramcecium, and Vorticella there 
are thousands of other Protozoa. Most of them live in 
water, but a few live in damp sand or moss, and some 
live inside the bodies of other animals as parasites. Of 
those which live in water some are marine, while others 
are found only in fresh-water streams and lakes. 



7§ 



ELEMENTARY ZOOLOGY 



Form of body. — The Protozoa all agree in having the 
body composed for its whole lifetime of a single cell,* 
but they differ much in shape and appearance. Some of 
them are of the general shape and character of Amoeba, 
sending out and retracting blunt, finger-like pseudopodia, 
the body-mass itself having no fixed form or outline but 




Fig. 9. — Sun animalcule, a fresh-water protozoan with a siliceous skeleton, 
and long thread-like protoplasmic prolongations. (From life.) 

constantly changing. Others have the body of definite 
form, spherical, elliptical, or flattened, enclosed by a thin 
cuticle, and having a definite number of fine thread-like 
or hair-like protoplasmic prolongations called flagella or 



* In some Protozoa a number of simitar cells temporarily unite to form a 
colony, but each cell may still be regarded as an individual animal. 



BRANCH PROTOZOA: THE ONE-CELLED ANIMALS 79 



cilia. Many of the familiar Protozoa of the fresh-water 
ponds always have two whiplash-like flagella projecting 
from one end of the body. By means of the lashing of 
these flagella in the water the tiny creature swims about. 
Others have many hundreds of fine short cilia scattered, 
sometimes in regular rows, over the body-surface. The 
Protozoan swims by the vibration of these cilia in the 
water. 

There is no stagnant pool, no water standing exposed 
in watering-trough or bar- 
rel which does not contain 
thousands of individuals of 
the one-celled animals. 
And in any such stagnant 
water there may always be 
found several or many dif- 
ferent kinds or species. A 
drop of this water examined 
with the compound micro- 
scope will prove to be a 
tiny w r orld (all an ocean) 
with most of its animals and 
plants one-celled in struc- 
ture. A few many-celled 
animals will be found in it 
preying on the one-celled 
ones. There are sudden FlG \ IO -- 
and violent deaths here, and 




births (by fission of the 
parent) and active locomo- 
tion and food-getting and 
growth and all of the busi- 



Stentor 
which may be fixed, like Vorticella, 
or free-swimming, at will, and 
which has the nucleus in the shape 
of a string or chain of bead-like 
bodies. The figure shows a single 
individual as it appeared when fixed, 
with elongate, stalked body, and as 
it appeared when swimming about, 
with contracted body. (From life.) 



nesses and functions of life 

which we are accustomed to see in the more familiar 

world of larger animals. 



So ELEMENTARY ZOOLOGY 

Marine Protozoa. — One usually thinks of the ocean as 
the home of the whales and the seals and the sea-lions, and 
of the countless fishes, the cod, and the herring, and the 
mackerel. Those who have been on the seashore will 
recall the sea-urchins and starfishes and the sea-anemones 
which live in the tide-pools. On the beach there are the 
innumerable shells, too, each representing an animal 
which has lived in the ocean. But more abundant than 
all of these, and in one way more important than all, 
are the myriads of the marine Protozoa. 

Although the water at the surface of the ocean appears 
clear and on superficial examination seems to contain no 
animals, yet in certain parts of the ocean (especially in 
the southern seas) a microscopical examination of this 
water shows it to be swarming with Protozoa. And not 
only is the water just at the surface inhabited by one- 
celled animals, but they can be found in all the water from 
the surface to a great depth below it. In a pint of this 
ocean-water there may be millions of these minute 
animals. In the oceans of the world the number of them 
is inconceivable. And it is necessary that these Protozoa 
exist in such great numbers, for they and the marine one- 
celled plants (Protophyta) supply directly or indirectly 
the food for all the other animals of the ocean. 

Among all these ocean Protozoa none are more in- 
teresting than those belonging to the two orders Forami- 
nifera (fig. 11) and Radiolaria. The many kinds belong- 
ing to these orders secrete a tiny shell (of lime in 
the Foraminifera, of silica in the Radiolaria) which en- 
closes most of the one-celled body. These minute shells 
present a great variety of shape and pattern, many being 
of the most exquisite symmetry and beauty. The shells 
are perforated by many small holes through which project 
long, delicate, protoplasmic pseudopodia. These fine 
pseudopodia often interlace and fuse when they touch each 



BRANCH PROTOZOA: THE ONE-CELLED ANIMALS 81 

other, thus forming a sort of protoplasmic network outside 
of the shell. In some cases there is a complete layer of 
protoplasm — part of the body protoplasm of the Protozoan 
— surrounding the cell externally. 

When these tiny animals die their hard shells sink to 
the bottom of the ocean, and accumulate slowly, in in- 
conceivable numbers, until they form a thick bed on the 
ocean floor. Large areas of the bottom of the Atlantic 







Fig. ii. — Rosalina varians, a marine protozoan (Foraminifera) with calca- 
reous shell. (After Schultze.) 

Ocean are covered with this slimy ooze, called Forami- 
nifera ooze or Radiolaria ooze, depending on the kinds of 
animals which have formed it. Nor is it only in present 
times that there has been a forming of such beds by the 
marine Protozoa. All over the world there are thick 
rock strata composed almost exclusively of the fossil shells 
of these simplest animals. The chalk-beds and cliffs of 
England, and of France, Greece, Spain, and America, 
were made by Foraminifera. Where now is land were 
once oceans the bottoms of which have been gradually 



82 ELEMENTARY ZOOLOGY 

lifted above the water's surface. Similarly the rock 
called Tripoli found in Sicily and the Barbadoes earth 
from the island of Barbadoes are composed of the shells 
of ancient Radiolaria. 

It is thus evident that the Protozoa is an ancient group 
of animals. As a matter of fact zoologists are certain 
that it is the most ancient of all animal groups. All of 
the animals of the ocean depend upon the marine Protozoa 
and the marine Protophyta, one-celled plants, for food. 
Either they feed on them directly, or prey on animals 
which in turn prey on these simplest organisms. A well- 
known zoologist has said: "The food-supply of marine 
animals consists of a few species of microscopic organisms 
which are inexhaustible and the only source of food for all 
the inhabitants of the ocean. The supply is primeval as 
well as inexhaustible, and all the life of the ocean has 
gradually taken shape in direct dependence on it.' The 
marine Protozoa are the only animals which live in- 
dependently; they alone can live or could have lived in 
earlier ages without depending on other animals. They 
must therefore be the oldest of marine animals. By 
oldest is meant that their kind appeared earliest in the 
history of the world, and as it is certain that ocean life is 
older than terrestrial life — that is, that the first animals 
lived in the ocean — it is obvious that the marine Protozoa 
are the most ancient of all animal groups. 

As already learned in the examination of examples of 
one-celled animals, it is evident that life may be success- 
fully maintained without a complex body composed of 
many organs performing their functions in a specialized 
way. The marine Protozoa illustrate this fact admirably. 
Despite their lack of special organs and their primi- 
tive way of performing the life-processes, that they live 
successfully is shown by their existence in such extraor- 
dinary numbers. They outnumber all other animals, 



BRANCE PROTOZOA: THE ONE-CELLED ANIMALS S3 

The conditions of life in the surface-waters of the ocean 
are easy and constant, and a simple structure and simple 
method of performing the necessary life-processes are 
wholly adequate for successful life under these con- 
ditions. 



CHAPTER XVI 
BRANCH PORIFERA: THE SPONGES 

THE FRESH- WATER SPONGE (Spongilla sp.) 

Technical Note. — Fresh-water sponges may perhaps not be 
readily found in the neighborhood of the school, but they occur 
over most of the United States, and careful searching will usually 
result in the finding of specimens. They are compact, solid-looking 
masses, sometimes lobed, resting on and attached to rocks, logs, 
timbers, etc., in clear water in creeks, ponds, or bayous. They 
are creamy, yellowish-brown or even greenish in color and resemble 
some cushion-like plant far more than any of the familiar animal 
forms. They can be distinguished from plants, however, by the 
fact that there are no leaves in the mass, nor long thread-like fibres 
such as compose the masses of pond algse (pond scum). When 
touched with the fingers a gritty feeling is noticeable, due to the 
presence of many small stiff spicules. Sponges should be removed 
entire from the substance they are attached to, and may be taken 
alive to the laboratory. They die soon, however, and should be put 
into alcohol before decay begins. 

Note the form of the sponge mass. Is it lobed or 
branched ? Examine the surface for openings. These 
are of two sizes; the larger are osteoles or exhalant open- 
ings, while the smaller and more numerous are pores or 
inlialant openings. The sponge-flesh is called sarcode. 
Examine a bit of sarcode under the microscope; note the 
spicules. Have these spicules a regular arrangement ? 
Of what are they composed ? 

Draw the entire sponge, showing shape and openings; 
draw some of the spicules. 

Embedded in the body-substance, especially near the 
base, note (if present) numerous small, yellowish, sub- 

8 4 



BRANCH PORIFERA: THE SPONGES S5 

spherical or disk-like bodies, the gemimdes. These are 
reproductive bodies. Each gemmule is a sort of internal 
bud. It is composed of an interior group of protoplasmic 
cells, enclosed by a crust thickly covered with spicules. 
In winter the sponge dies down and the gemmules are set 
free in the water. In spring the protoplasmic contents 
issue through an aperture in the crust, called the micro- 
pyle or foraminal opening, and develop and grow into a 
new sponge. 

For a good account of the fresh-water sponge, see 
Pott's "Fresh-water Sponges." 

A CALCAREOUS OCEAX-SPOXGE (Grantia sp.) (fi gj 7, D, E, F.) 

Technical Note. — For inland schools, specimens preserved in 
alcohol or formalin must be used. They may be obtained from 
dealers in naturalists' supplies (see. p. 453;. Specimens of some 
species of this genus can be obtained at almost any point on the 
Atlantic or Pacific coasts of this country. 

Examine the external structure of a specimen. Note 
the elongate, sub-cylindrical form, the attached base, the 
free end. Note the large exhalant opening, osteole or 
osculnm, at the free end; the numerous small inhalant 
openings elsewhere on the surface (best seen in dried 
specimens). Note the spicules covering the surface of the 
body, and the longer ones surrounding the osculum. Cut 
the sponge in two longitudinally and note the simple cylin- 
drical body-cavity, the gastric cavity or cloaca. Note the 
thickness of the body- wall ; note the tubes running through 
the body-wall from cloaca to external surface. Through 
these tubes water laden with food enters the gastric cavity, 
where the food is digested, the water and undigested 
particles passing out through the osculum. Crush a bit of 
dried sponge, or boil a bit of soft sponge in caustic potash 
and mount on a glass slide. Examine under a micro- 
scope and note the abundance of spicules and the variety 
in their form. Two kinds may always be found, and 



86 ELEMENTARY ZOOLOGY 

sometimes three. These spicules are composed of car- 
bonate of lime and can be dissolved by pouring on to 
them a drop of hydrochloric acid. 

Some of the sponges may have buds growing out from 
them near the base. These buds are young sponges 
developed asexually. If allowed to develop fully the 
buds would have detached themselves from the parent 
and each would have become a new sponge. 

Make drawings showing the form of a whole sponge ; 
the appearance of the inner face of the sponge bisected 
longitudinally; the shape of the spicules. 

A COMMERCIAL SPONGE 

Technical Note. — For the study of the skeleton of an ocean- 
sponge with more complex body buy several common small bath- 
sponges without large holes running entirely through them. The 
teacher should have also a few specimens of small marine sponges 
preserved in alcohol or formalin. Such specimens should be part 
of the laboratory equipment (see account of laboratory equipment, 
p. 450), and can be readily and cheaply obtained from dealers in 
naturalists' supplies. 

The bath-sponge or slate-sponge consists simply of the 
hard parts or skeleton of a sponge animal. In life all of 
the skeleton is enclosed or covered by a soft, tough mass 
composed of layers of cells. Note the many openings on 
the surface of the sponge. Crush a bit of the skeleton 
and examine it under the microscope. Note that it is 
composed of fine fibres of a tough, horny substance called 
spongin, instead of tiny distinct calcareous spicules. 

OTHER SPONGES 

The sponges are fixed, plant-like aquatic animals. 
The members of a single family live in fresh water, being 
found in lakes, rivers, and canals in all parts of the world. 
All the other sponges, and there are several thousand 
species known, live in the ocean. They are to be found 
at all depths, some in shallow water near the shore and 



BRANCH PORIFERA: THE SPONGES 



others in deeper water, even to the deepest depths yet 
explored. They are found in all seas, though especially 
abundantly in the Atlantic Ocean and Mediterranean Sea. 
Form and size. — The shape of the simplest sponges is 
that of a tiny vase or nearly cylindrical cup, hollow and 
attached at its base. At the free end there is a large 
opening. But there is a great deal of variety in the form 
and size of different sponges. 
There is, indeed, much varia- 
tion in the shape and general 
character of different individuals 
of the same species. Unlike 
most other animals, sponges are 
fixed, and the character of the 
surface to which a sponge is 
attached has much influence 
upon its shape. If this surface 
is rough and uneven the sponge 
may follow in its growth the 
sinuosities of the surface and so 
become uneven and distorted 
in shape. At best, only a few 
kinds of sponges have any very 
even and symmetrical shape. 
Most of them are very unsym- 
metrical and grow more like a 
low compact bushy plant than 
like the animals we are familiar 
with. The smallest sponges 
are only I mm. (^ in.) high, 
while the largest may be over FlG - 12. — The skeleton of a 

. '-glass" sponge (skeleton com- 

a meter (39 in.) in height. In poS ed of siliceous spicules) from 
color living sponges may be J a P :m - (From specimen.) 
red, purple, orange, gray, and sometimes blue. Most 
sponges have the whole body of one color. 




SS ELEMENTARY ZOOLOGY 

Skeleton. — A very few sponges have no skeleton at 
all. The others have a skeleton or hard parts composed 
of interwoven fibres of the tough, horny substance called 
spongin, or of hosts of fine needles or spicules of silica or 
of carbonate of lime. The siliceous skeletons of some 
of the so-called glass-sponges (fig. 12) are very beautiful. 
The lime and siliceous sponge spicules exhibit a great 
variety of outline, some being anchor-shaped, some cross- 
shaped, and some resembling tiny spears or javelins. 

Structure of body. — The skeleton of a sponge whether 
composed of interlacing fibres or of short spicules is 
always invisible from the outside when the sponge is alive. 
It is embedded in, or clothed by, the soft, fleshy part of 
the body. The soft part of the sponge is composed 
simply of two layers of cells, one constituting the external 
surface of the body, and the other lining the interior 
cavities and canals of the body. Between these two cell- 
layers there is a mass of soft gelatinous substance all 
through which protoplasm ramifies, and in which are em- 
bedded numerous scattered cells. There are, as seen in 
the case of Spongilla and Grantia, no systems of organs 
such as characterize the higher animals. No heart, lungs, 
alimentary canal, nervous system, organs of locomotion, 
eyes, ears, or other organs of special sense; the sponge 
has none of these. It is simply an aggregate of cells, 
arranged in two layers, and supported usually by a skele- 
ton of horny fibres or calcareous or siliceous spicules. Its 
body is usually shapeless, unsymmetrical and without 
front or back, right or left. It is not to be wondered at 
that sponges were for a long time believed to be plants. 

Feeding habits. — The sponges feed on minute bits of 
animal or plant substance and on the microscopic unicel- 
lular plants or animals which float in the water which 
bathes their bodies. The water entering the sponge- 
body through the various openings of the surface is moved 



BRANCH PORIFERA: THE SPONGES 89 

along by the waving or lashing of the flagella of the cells 
which line the canals, and these currents of water bear 
with them the tiny organisms which are taken up by these 
same cells and digested. The incoming currents of water 
meet in the central cavity or cavities of the body and pass 
.out through the large opening called the osculum at the 
free end of the vase-like body, or if the body is branched, 
through the large openings at the tips of these branches. 

The same currents of water bring also oxygen for the 
sponge's breathing and carry away the carbonic acid gas 
given out by the body-cells. 

As a German naturalist has said, the one necessary 
condition for the life of a sponge is the streaming of water 
through its body. All sponges have a system of canals 
for this water-current and all have means, in the waving 
flagella or cilia with which these canals are lined, for pro- 
ducing these currents. When a live sponge is put into a 
vessel of water, currents are immediately set up, and they 
always flow into the body through the many fine openings 
and out of the body through the osculum. 

Development and life- history. — Although the sponge 
in its adult condition is permanently attached by its base 
to the sea-bottom or to some rock or shell, when it is first 
born it is an active free-swimming creature. The sponges 
reproduce in two ways, asexually and sexually. The 
asexual mode of reproduction of the fresh-water sponge 
by gemmules has already been described. The ocean 
sponges also reproduce asexually either by forming 
interior gemmules or external buds. In this latter 
method a bud forms on the outer surface of the body 
which increases in size and finally grows into a new 
sponge individual. In some species this new sponge does 
not become separated from the body of the mother, 
but remains attached to it like a branch to a tree-trunk. 
By the continued production of such non-separating indi- 



90 ELEMENTARY ZOOLOGY 

viduals, a colony of sponges is formed which has the 
general appearance of a branching plant. In other 
species the new sponge formed by the development and 
growth of a bud falls off and becomes a distinct separate 
individual. 

In the sexual mode of reproduction, male or sperm- 
cells and female or egg-cells are developed in the same 
individual. The sperm-cells are motile and swim about 
in the cavities and canals of the sponge-body until they 
find egg-cells,, which they fertilize. The fertilized eggs 
begin to develop and pass through their first stages in the 
sponge-body. Finally the embryo sponge, which is 
usually a tiny oval or egg-shaped mass of cells, escapes 
from the body of the parent into the water. The young 
sponge has some of its outer cells provided with cilia, 
and by means of these it swims about. After a while 
it comes to rest on the ocean-floor or on some rock 
or shell, attaches itself, and begins to take on the form 
and character of the parent. It leads hereafter a fixed 
sedentary life. 

The sponges of commerce. — The sponge-skeletons 
which are the " sponges " that we use all belong to a few 
species, not more than half a dozen. Most of the com- 
mercial sponges come from the Mediterranean Sea, though 
some come from the Bahama Islands, some from the Red 
Sea, and a few from the coasts of Greece, Asia Minor, 
and Africa. The commercial sponges do not live in very 
deep water; they are usually found not deeper than 200 
feet. The living sponges are collected by divers, or are 
dragged up by men in boats using long-poled hooks, or 
dredges. ''When secured they are exposed to the air 
for a limited time, either in the boats or on shore, and 
then thrown in heaps into the water again in pens or 
tanks built for the purpose. Decay thus takes place with 
great rapidity, and when fully decayed they are fished up 



BRANCH PORIFERA: THE SPONGES 91 

again, and the animal matter beaten, squeezed, or washed 
out, leaving the cleaned skeleton ready for the market. 
In this condition after being dried and sorted, they are 
sold to the dealers, who have them trimmed, re-sorted 
and put up in bales or on strings ready for exportation. 
There are many modifications of these processes in differ- 
ent places, but in a general way these are the essentia- 
steps through which the sponge passes before it is con- 
sidered suitable for domestic purposes. Bleaching- 
powders or acids are sometimes used to lighten the color, 
but these unless very delicately handled injure the dura- 
bility of the fibres. " 

Classification. — The sponges are classified according 
to the character of the skeleton. In one group are put 
all those sponges which have a skeleton of calcareous 
spicules, and this group is called the Calcarea. All other 
sponges are grouped as Non-Calcarea, the members of 
this group either having no skeleton at all, or having a 
skeleton composed of siliceous spicules or of spongin 
fibres. According to the absence or presence of a skele- 
ton and the character of the skeleton when it exists the 
Non-Calcarea are subdivided into smaller groups. 



CHAPTER XVII 

BRANCH CCELENTERATA: THE POLYPS, SEA- 
ANEMONES, CORALS, AND JELLYFISHES 

The structure and life-history of an example of the 
polyps (the Fresh-water Hydra, Hydra sp.) has been 
studied in Chapters X and XL 

OTHER POLYPS, SEA- ANEMONES, CORALS, AND 

JELLYFISHES 

Technical Note. — The teacher should have, if possible, several 
pieces of coral and a few specimens of Coelenterates in alcohol or 
formalin, which will show the external character, at least, of these 
animals (see account of laboratory equipment, p. 450). If the 
school is on the coast, the pupils should be shown the sea-anemones 
of the tide-pools. 

The animals which are included in the branch Ccelen- 

terata are, at least in living condition, unfamiliar to most 

of us. Like the sponges, they are almost all inhabitants 

of the ocean; a few, like Hydra, live in fresh water. 

Like the sponges, too, most of the members of this 

branch are fixed, and in their general appearance suggest 

a plant rather than an animal. The name zoophytes, or 

plant-animals, which is often applied to these animals is 

based on this superficial resemblance. But many of the 

Coelenterates lead an active free-swimming life. This is 

true of the jellyfishes which float or swim about on or near 

the surface of the ocean. Many of the zoophytes spend 

part of their life in an active free-swimming condition 

before settling down, becoming attached and thereafter 

92 



BRANCH CCELENTERATA: THE POLYPS, ETC. 93 

remaining fixed. In localities near the seashore many 
animals belonging to this great group can be readily 
found and observed. The beautiful sea-anemones with 
their slowly-waving tentacles, the fine many-branched 
truly plant-like hydroids with their hosts of little buds, 
and the soft colorless masses of jelly, the jellyfishes, which 
are cast up on to the beaches by the waves are all animals 
belonging to the branch Coelenterata. 

General form and organization of body. — The general 
or typical plan of body-structure for the Coelenterata, 
these animals which come next to the sponges in degree 
of complexity, can best be understood by imagining the 
typical cylindrical or vase-like body of the simple sponges 
to be modified in the following way: The middle one of 
the three layers of the body-wall not to be composed of 
scattered cells in a gelatinous matrix, but to be simply a 
thin non-cellular membrane ; the body-wall not to be 
pierced by fine openings or pores, but connected with the 
outside only by the single large opening at the free end, 
and this opening to be surrounded by a circlet of arm-like 
processes or tentacles, which are continuations of the 
body-wall and similarly composed. Such a body-struc- 
ture, w r hich we saw well shown by Hydra, is the funda- 
mental one for all polyps, sea-anemones, corals, and 
jellyfishes. The variety in shape of the body and the 
superficial modifications of this type-plan are many and 
striking, but after all the type-plan is recognizable through- 
out the whole of this great group of animals. 

The two chief body-shapes represented in the branch 
are those of the polyps on the one hand, and the jelly- 
fishes or medusae on the other. The polyp-shape is that 
of a tube with a basal end blind or closed, attached to 
some firm object in the water and with the free end with 
an opening, the mouth-opening. At this mouth-end 
there is a circlet of movable, very contractile tentacles. 



94 ELEMENTARY ZOOLOGY 

The mouth may open directly into the interior of the body, 
which interior may be called the digestive cavity, or it 
may lead into a simple short tube produced by the in- 
vagination or bending in of the body-wall, which may be 
looked on as the simplest kind of oesophagus. This 
oesophageal tube opens into the body-cavity or digestive 
cavity. This cavity may be incompletely divided by 
longitudinal partitions which project from the sides into 
the cavity. 

The jellyfish or medusoid body-form corresponds in 
general to an umbrella or bell. Around the edge of this 
umbrella are disposed numerous threads or tentacles 
(corresponding to the circlet of tentacles in the polyp). 
The mouth-opening is at the end of a longer or shorter 
projection which hangs down from the middle of the 
under side of the umbrella. The interior body-cavity or 
digestive cavity extends out into the umbrella-shaped 
part of the body, usually in the condition of canals radiat- 
ing from the centre and a connecting canal running 
around the margin of the umbrella. 

Structure. — Although the Coelenterata show little in- 
dication of the complex composition of the body out of 
organs, as it exists among the higher animals, yet they 
do show an unimstakable advance on the simple, almost 
organless body of the sponges. This is chiefly shown by 
the differentiation among the cells which compose the 
body. In the polyps and jellyfishes some of the cells are 
specialized to be unmistakable muscle-cells, some to be 
nerve-cells and fibres, and so on. A very simple nervous 
system consisting of small groups of nerve-cells connected 
by nerve-fibres exists. Some very simple special sense- 
organs may occur. The digestive system, although in 
the simpler Ccelenterates consisting merely of the cylin- 
drical body-cavity enclosed by the body-wall and opening 
by the single hole at the free end of the body, in some is 



BRANCH CCELENTERATA : THE POLYPS, ETC. 95 

rather complex and is composed of different parts. Those 
Coelenterates which are not fixed but lead an active, free- 
swimming life, viz., the jellyfishes or medusae, are the 
most highly organized. 

The tentacles which surround the mouth-opening and 
serve to grasp food and carry it into the mouth, and the 
stinging or lasso threads with which these tentacles are 
provided are special organs possessed by most of these 
animals. 

Skeleton. — Like the sponges, some of the Coelenterata 
possess a hard skeleton. This skeleton is always com- 
posed of calcium carbonate and is called coral. Those 
polyps which form such a skeleton are called the corals. 
Coral will be described in connection with the account of 
the coral-polyps. 

Development and life-history. — The polyps and jelly- 
fishes reproduce both asexually and sexually. The 
asexual mode is usually that of budding. On a polyp a 
bud is formed by a hollow outgrowth of the body-wall. 
The bud grows, an opening appears at its distal end, a 
circlet of tentacles arises about this mouth-opening and a 
new polyp individual is formed. This individual may 
separate from the parent or it may remain attached to it. 
By the development of numerous buds, and the remaining 
attached of all of the individuals developing from these 
buds, a colony of polyp individuals may be formed, plant- 
like in appearance. The various polyp individuals of a 
colony may differ somewhat among themselves, and these 
differences are correlated with a division of labor. Thus 
some of the individuals may devote themselves to getting 
food for the colony, and these have mouth and tentacles. 
Others may be devoted to the production of new indi- 
viduals by budding or by producing germ-cells, and may 
not have any mouth-opening or any food-grasping 
tentacles. 



96 ELEMENTARY ZOOLOGY 

In case of many polyps all or some of the new indi- 
viduals which arise by budding do not become polyps, but 
develop into medusae or jellyfish, which separate from the 
fixed polyp and swim off through the water. These 
medusae or jellyfish produce sperm-cells and egg-cells. 
The sperm-cells fertilize the egg-cells and a new indi- 
vidual develops from each fertilized egg. This new indi- 
vidual is at first an active free-swimming larva called a 
planula, which does not resemble either a medusa or polyp. 
After a while it settles down, becomes fixed and develops 
into a polyp. Thus a polyp may produce a medusa or 
jellyfish which, however, produces not a new jellyfish, but 
a polyp. This is called an alternation of generations, 
and is not an uncommon phenomenon among the lower 
animals. It results from such an alternation of genera- 
tions that a single species of animal may have two distinct 
forms. This having two different forms is called dimor- 
phism. Sometimes, indeed, a species may appear in 
more than two different forms ; such a condition is called 
polymorphism. 

Not all medusae or jellyfish are produced by polyp indi- 
viduals, nor do jellyfish always produce polyps and not 
jellyfishes. There are some jellyfishes (we might call 
them the true jellyfishes) which always have the jellyfish 
form, producing new jellyfishes either by budding or by 
eggs, and there are some polyps which always have the 
true polyp form, producing new individuals, either by 
budding or by eggs, always of polyp form and never of 
jellyfish form. That is, some species of Ccelenterata 
exist only in polyp form, some species exist only in jelly- 
fish form, while some species (those having an alternation 
of generations) exist in both polyp and jellyfish form, 
these two forms appearing as alternate generations. 

Classification. — The branch Coelenterata is divided 
into four classes: (i) the Hydrozoa, including the fresh- 



BRANCH CCELENTERATA : THE POLYPS, ETC. 



97 




water polyps, numer- 
ous marine polyps, 
many small jellyfishes 
and a few corals; (2) 
the Scyphozoa, includ- 
ing most of the large 
jellyfishes ; (3) the Ac- 
tinozoa, including the 
sea-anemones and 
most of the stony 
corals; (4) the Cte- 
nophora, including 
certain peculiar jelly- 
fishes. 

The polyps, colonial 
jellyfishes, etc. (Hy- 
drozoa). — To the class 
Hydrozoa belongs the 
Hydra already studied. 
There are a few other 
fresh-water polyps and 
they all belong to this 
class. The most in- 
teresting members of 
the class are the " co- 
1 o n i a 1 jellyfishes, " 
constituting the order 
Siphonophora. These 



Fig. 13. -The Portuguese Man-of-War {Physalia sp.). 

from Atlantic Coast. ) 



(From specimen 



9^ ELEMENTARY ZOOLOGY 

colonial je-llyfishes are floating or swimming colonies of 
polypoid and medusoid individuals in which there is a 
marked division of labor among the individuals, ac- 
companied by marked differences in structural charac- 
ter. The individuals are accordingly polymorphic, 
that is, appear in various forms, although all belong 
to the same species. Because these various individuals 
forming a colony have given up very largely their 
individuality, combining together and acting together like 
the organs of a complex animal, they are usually not 
called individuals, nor on the other hand organs, but 
zooids y or animal-like structures. The beautiful "Portu- 
guese man-of-war " (fig. 13) is one of these colonial jelly- 
fishes. It appears as a delicate bladder-like float, brilliant 
blue or orange in color, usually about six inches long, 
and bearing on its upper surface which projects above the 
water a raised parti-colored crest, and on its under surface 
a tangle of various appendages, thread-like with grape- 
like clusters of little bell- or pear-shaped bodies. Each 
of these parts is a peculiarly modified polyp- or medusa- 
zooid produced by budding from an original central zooid. 
The Portuguese man-of-war is very common in tropical 
oceans, and sometimes vast numbers swimming together 
make the surface of the ocean look like a splendid flower- 
garden. 

Usually the central zooid in a Siphonophore to which 
the other zooids are attached is not a bladder-like float, 
but is an upright tube of greater or less length. In the 
Siphonophore shown in figure 14, the compound body is 
composed of a long central hollow stem with hundreds 
or thousands of variously shaped parts, each of which is 
reducible to either a polyp or medusazooid, attached 
around it. The upper end is enlarged to form an air- 
filled chamber, a sac-like boat, by means of which the 
whole colony is kept afloat. Around the upper end of the 



BRANCH CCELENTERATA: THE POLYPS, ETC. 



99 



central stem are many medusoid structures^ the swimming- 
bells, by means of _ 

whose opening and 
closing the whole col- 
ony is made to swim 
through the water. 
Each swimming - bell 
is a modified medusa- 
zooid, without tenta- 
cles, without digestive 
or reproductive or- 
gans, but exercising 
the power of swim- 
ming by contracting 
and forcing the water 
out of the hollow bell 
just as is done by 
the free medusae. Be- 
low the swimming- 
bells, at the lower end 
of the central stem, 
are grouped many 
structures presenting 
at first sight a confu- 
sion of variety and 
complexity, but on 
careful examination 
revealing themsel ves 
to be polyp- and me- 
dusa-zooids modified 
to form at least five 

kinds of particularly 

r . . Fig. 14. — A colonial jellyfish (Siphonophora). 

functioning Struc- (After Haeckel.) 

tures. There are many flattened scale-like parts whose 
function is simply that of affording a passive protection, 
LofC. 




ioo ELEMENTARY ZOOLOGY 

in times of danger, to the other structures. These pro- 
tecting-scales are greatly modified medusa-zooids, each 
consisting of a simple cartilage-like gelatinous mass 
penetrated by a food-carrying canal. Under the broad 
leaves of these protecting-zooids are a number of pear- 
shaped bodies which have a wide octagonal mouth-open- 
ing at their free end, and possess in their interior certain 
digestive glands. Each one is provided with a very long 
flexible tentacle which bears many fine stinging-threads. 
The tentacle waves back and forth in the water, and 
on coming in contact with an enemy or with prey its 
poisonous stinging-threads shoot out and paralyze or 
wound the unfortunate animal. These pear-shaped bodies 
are the feeding structures, each being a modified polyp- 
zooid. Scattered among these dangerous structures are 
many somewhat similarly shaped but wholly harmless 
structures, the sense-structures. Each of these has a 
pear-shaped body but without mouth-opening, and also 
a long, very sensitive, tentacle-like process. The sense 
of feeling is highly developed in these tentacles, and they 
discover for the colony the presence of any strange body. 
These sense-structures are modified polyp-zooids. Finally 
there are two other kinds of structures, usually arranged 
in groups like bunches of grapes, which are the repro- 
ductive structures, male and female. They are modified 
medusa-zooids grown together and without tentacles. 
This whole colony, or this compound animal, floats or 
swims about at the surface of the ocean, and performs all 
of the necessary functions of life as a single animal com- 
posed of organs might. Yet the Siphonophore is more 
truly to be regarded as a community in which the hundreds 
or thousands of animals, representing five or six kinds of 
individuals, all of one species, are fastened together. Each 
individual performs the particular duties devolving upon 
its kind or class. Thus there are food-gathering indi- 



BRANCH CCELENTERATA : THE POLYPS, ETC. ior 

viduals, locomotor individuals, sense individuals, and 
reproductive individuals. The modifications of the various 
Kinds of individuals are more extreme than in the case of 
the various kinds of individuals composing a bee-com- 
munity, for example, but the holding together or fusing 
of all into one body or corporation is a condition which 
makes this greater modification necessary and not un- 
expected. And there is no difficulty in seeing that each 
of these parts is really, structurally considered, a modified 
polyp or medusa. 

The large jellyfishes, etc. (Scyphozoa).— To the class 
Scyphozoa belong most of the common large jellyfishes. 




Fig. 15. — A jellyfish or medusa. Gon'onema vertens, eating two small 
fishes. (From specimen from Atlantic Coast,) 

When one walks along the sea-beach soon after a storm 
one may find many shapeless masses of a clear jelly-like 



io2 ELEMENTARY ZOOLOGY 

substance scattered here and there on the sand. These 
are the bodies or parts of bodies of jellyfishes which have 
been cast up by the waves. Exposed to the sun and 
wind the jelly-like mass soon dries or evaporates away to 
a small shrivelled mass. The body-substance of a jelly- 
fish contains a very large proportion of water; in fact 
there is hardly more than I per cent of solid matter in it. 

The jellyfishes occur in great numbers on the surface of 
the ocean and are familiar to sailors under the name of 
"sea-bulbs.' Some live in the deeper waters; a few 
specimens have been dredged up from depths of a mile 
below the surface. They range in size from " umbrellas " 
or disks a few 7 millimeters in diameter to disks of a 
diameter of two meters (2\ yards). They are all car- 
nivorous, preying on other small ocean animals which 
they catch by means of their tentacles provided with 
stinging-threads. The tentacles of some of the largest 
jellyfishes "reach the astonishing length of 40 meters, or 
about 130 feet.' Many of the jellyfishes are beautifully 
colored, although all are nearly transparent. Almost all 
of them are phosphorescent, and when irritated some 
emit a very strong light. 

The sea-anemones and corals (Actinozoa). — Almost 
everywhere along the seashore where there are rocks and 
tide-pools a host of various kinds of sea-anemones can be 
found. When the tide is out, exposing the dripping sea- 
weed-covered rocks, and the little sand- or stone-floored 
basins are left filled w T ith clear sea-water, the brown and 
green and purple "sea-flowers " may be found fixed to 
the rocks by the base with the mouth-opening and circlet 
of slowly-moving tentacles hungrily ready for food 
(fig. 16). Touch the fringe of tentacles with your finger- 
tip and feel how they cling to it and see how they close in 
so as to carry what they feel into the mouth-opening. A 
host of individuals there are, and scores of different kinds; 



BRANCH CCELENTERATA : THE POLYPS, ETC. 



io3 



some small, some large, some with the bod}' covered out- 
side with tiny bits of stone and shell so that they are 
hardly to be distinguished from the rock to which they 




Fig. 16. — Sea anemones, Bunodes calif ornica, open and closed individuals. 
The closed individuals in upper right-hand corner show the external 
covering of small bits of rock and shell, characteristic of most individu- 
als of this species. (From living specimens in a tide-pool on the Bay 
of Monterey, California.) 



cling; 



some of bright and showy colors. These are the 
most familiar members of the class Actinozoa. 

But in other oceans, along the coasts of other lands, 
especially those of the tropics and sub-tropics, there are 



104 ELEMENTARY ZOOLOGY 

some other members of the class which are of unusual 
interest. They are the corals, or coral polyps. We 
know these animals chiefly by their skeletons (fig. 17). 
The specimens of corals which one sees in collections, or 
made into ornaments, are the calcareous skeletons of 
various kinds of the coral polyps. Some of the corals 
live together in enormous numbers, forming branching 
colonies fixed as closely together as possible, and secrete 
while living a stony skeleton of carbonate of lime. These 
skeletons persist after the death of the animals, and 
because of their abundance and close massing form great 
reefs or banks and islands. These coral reefs and islands 
occur only in the warmer oceans. In the Atlantic they 
are found along the coasts of Southern Florida, Brazil 
and the West Indies; in the Pacific and Indian Oceans 
there are great coral reefs on the coast of Australia, 
Madagascar and elsewhere, and certain large groups of in- 
habited islands like the Fiji, Society, and Friendly Islands 
are exclusively of coral formation. Coral islands have a 
great variety of form, although the elongated, circular, 
ring-shaped and crescent forms predominate. How such 
islands are first formed is described as follows by a well- 
known student of corals: 

"A growing coral plantation, with its multitudinous 
life, oftentimes arises from great depths of the ocean, and 
the sea-bed upon which it rests is probably a submarine 
bank or mountain, upon which have lodged and slowly 
aggregated the hard skeletons of pelagic forms of life. 
When, through various sources of increase, this submarine 
bank approaches the depth of from one hundred to one 
hundred and fifty feet from the surface of the water, there 
begins on its top a most wonderful vital activity. It is 
then within the bathymetric zone of the reef-building 
corals. Of the many groups of marine life which then 
take possession of the bank, corals are not the only 



BRANCH CCELENTERATA : THE POLYPS, ETC. 105 

animals, but they are the most important, as far as its 
subsequent history goes. As the bank slowly rises by 
their growth, it at last approaches the surface of the 
water, and at low tide the tips of the growing branches 
of coral are exposed to the air. This, however, only 
takes place in sheltered localities, for long before it has 
reached this elevation it has begun to be more or less 




Fig. 17. — Skeleton of a branching coral, Madrepora cervicomis. (From 

specimen.) 



changed and broken by the force of the waves. As the 
submarine bank approaches the tide level, the delicate 
branching forms have to meet a terrific wave-action. 
Fragments of the branching corals are broken off from 
the bank by force of the waves, and falling down into the 
midst of the growing coral below fill up the interstices, 



106 ELEMENTARY ZOOLOGY 

and thus render the whole mass more compact. At the 
same time larger fragments are broken and rolled about 
by the waves and are eventually washed up into banks 
upon the coral plantation, so that the island now appears 
slightly elevated above the tides. This may be called a 
first stage in the development of a coral island. It is, 
however, little more than a low ridge of worn fragments 
of coral washed by the high tides and swept by the larger 
waves — a low, narrow island resting on a large submarine 
bank." 

When the coral island rises thus a little above the sur- 
face of the water, the waves break up some of the coral 
into fine sand, which fills in the interstices, and offers a 
sort of soil in which may germinate seeds brought in the 
dried mud on the feet of ocean birds or carried by the 
ocean currents. With the beginning of vegetable growth 
the soil is more firmly held, is fertilized and ready for the 
seeds of plants which need a better soil than lime sand. 
Flying insects find their way to the island, especially if 
it be near the mainland, birds begin to nest on it, and 
soon it may be the seat of a luxuriant plant and animal 
life. 

For an account of coral islands see Darwin's "The 
Structure and Distribution of Coral Reefs." 

There are over 2000 kinds of coral polyp known, and 
their skeletons vary much in appearance. Because of the 
appearance of the skeleton certain corals have received 
common names, as the organ-pipe coral, brain coral, etc. 
The red coral, of which jewelry is made, grows chiefly in 
the Mediterranean. It is gathered especially on the 
western coast of Italy, and on the coasts of Sicily and 
Sardinia. Most of this coral is sent to Naples, where it is 
cut into ornaments. 

There are other interesting members of the class 
Actinozoa like the beautiful sea-pens, sea-feathers and 



BRANCH CCELENTERATA : THE POLYPS, ETC. 107 

sea-fans, delicate, branching, tree-like forms found all 
over the world. 

Ctenophora. — The members of this class are mostly 
small, peculiar jellyfishes which do not form colonies, and 
are extremely delicate, being usually perfectly trans- 
parent. They swim by means of cilia. They never 
appear in a polyp condition, but are always medusoid in 
shape. 



CHAPTER XVIII 

BRANCH ECHINODERMATA : STARFISHES, 
SEA-URCHINS, SEA-CUCUMBERS 

STARFISH (Asterias sp.) 

Technical Note. — The species of Asterias are widely dis- 
tributed on both coasts of the United States and may be procured 
on almost any rocky shore at low tide. Teachers in inland schools 
can obtain preserved material from the dealers mentioned on p. 
453. Most of the specimens should be placed in alcohol or 4%' 
formalin. If fresh material can be had it is well to place at least 
one specimen for each student in a 20I solution of nitric acid in 
water for two or three hours, when all of the calcareous parts will 
have been dissolved, and after a thorough washing the specimen 
will be ready for use. 

External structure (figs. 18 and 19.) — In a fresh 
specimen or one which has been preserved in alcohol or 
formalin note the raying out of parts of the body from a 
common centre. This is characteristic of the body or- 
ganization of all Echinoderms, and is known as radial 
symmetry. The low r er surface of the body is called the 
oral (because the mouth is on this surface), while the 
upper is called the aboral surface. The central part of 
the body is called the disk. Note on the aboral surface 
of the disk a small striated calcareous plate, the madre- 
porite or madreporic plate. In the middle (or very 
nearly in the middle) of this surface of the disk there is 
a small pore, the anal opening. The entire aboral sur- 
face as well as a greater part of the oral side is thickly 
studded with the calcareous ossicles of the body-wall. 
These ossicles support numerous short stout spi7ies ar- 
ranged in irregular rows. Note that some of the ossicles 

108 



BRANCH ECHINODERMATA : STARFISHES, ETC. 109 

support certain very small pincer-like processes, the pedi- 
cellarice. In the interspaces between the calcareous plates 
are soft fringe-like projections of the inner body-lining, the 



•eye spot 



muscles of the pyloric caeca 




caecum 
muscles of the pyloric caeca 



eye spot'--' 



Fig. 18. — Dissection of a starfish {Asterias sp.). 

respiratory cceca. Note at the tip of each arm or ray a 
cluster of small calcareous ossicles and within each cluster 
a small speck of red pigment, the eye-spot or ocellus. 



no ELEMENTARY ZOOLOGY 

Make a drawing of the aboral surface showing all these 
parts. 

On the oral surface note the centrally-located mouth, 
the ambulacral grooves, one running longitudinally along 
each ray, and in each groove two double rows of soft 
tubular bodies with sucker-like tips. These are called 
the tube-feet and are organs of locomotion. Make a 
drawing of the oral surface. 

Internal structure (figs. 18 and 19).— Technical Note.— 
Take a specimen which has been immersed for some time in the nitric 
acid solution, and with a strong pair of scissors, or better, bone- 
cutters, cut away all the aboral wall of the disk except that immedi- 
ately around the madreporite and the anus. Now begin at the tip 
of each ray and cut away the aboral wall of each, leaving, however, 
a single arm intact. When the roof of each arm has been carefully 
dissected away the specimen should appear as in fig. 18. 

Note the large alimentary canal, which is divided into 
several regions. Note the short (Esophagus leading from 
the mouth on the oral surface directly into a large mem- 
branous pouch, the cardiac portion of the stomach. By 
a short constriction the cardiac portion is separated from 
the part w 7 hich lies just above, i.e., the pyloric portion of 
the stomach. From the pyloric portion large, pointed, 
paired glandular appendages extend into each ray. 
These are the pyloric cceca. Their function is digestive, 
and oftentimes they are spoken of as the digestive glands 
or "livers.' 1 The pyloric caeca, as well as the cardiac 
portion of the stomach, are held in place by paired muscles 
which extend into each arm. Note two sets of these 
muscles, one set for thrusting the cardiac portion of the 
stomach out through the mouth and another for pulling it 
back, the protractor muscles and retractor muscles, 
respectively. The starfish obtains its food by enclosing 
it in its everted stomach and then withdrawing stomach 
and food into the body. Note that the pyloric portion of 
the stomach opens above into a short intestine terminating 



BRANCH ECHINODERMATA : STARFISHES, ETC. in 

in the anus, and observe that there is attached to the in- 
testine a convoluted many-branched tube, the intestinal 
c cecum. 

Carefully remove a pair of pyloric caeca from one of the 
rays and note the short duct which connects them with 
the pyloric chamber of the stomach. Note in the angle 
of each two adjoining rays paired glandular masses which 
empty by a common duct on the aboral surface. These 
glands are the reproductive organs. Note the small bulb- 
like bladders extending in two double rows on the floor 
of each ray. These are the water-sacs or ampullce, and 
each one is connected directly with one of the locomotor 
organs, the tube-feet. 

Make a drawing of the organs in the dissection which 
have so far been studied. 

Technical Note. — For a careful study of the locomotor organs 
a fresh starfish should be injected. This can usually be accom- 
plished by cutting one ray off squarely, and inserting the needle of 
a hypodermic syringe (which has been previously filled with a 
watery solution of carmine or Berlin blue), into the end of the 
radial water-tube which runs along the floor of the ray. By 
injecting here, the whole system of vessels, tube-feet, and ampullae 
are filled. 

Note a ring-shaped canal which passes around the 
alimentary canal near the mouth from which radial vessels 
run out beneath the floor of each ray and from which a 
hard tube extends to the madreporite. This hard tube is 
the stone canal, so called because its walls contain a series 
of calcareous rings, while the circular tube is the ring 
canal or circum-oral zvater-ring from which radiate the 
radial canals. In some species of starfish there are 
bladder-like reservoirs, Polian vesicles, which extend 
interradially from the ring canal. 

Note that the ampullae and tube-feet are all connected 
with the radial canals. By a contraction of the delicate 



IT2 



ELEMENTARY ZOOLOGY 



muscles in the walls of the ampullae the fluid in the cavity 
is compressed, thereby forcing the tube-feet out. By the 
contraction of muscles in the tube-feet they are again 
shortened while the small disk-like terminal sucker clings 
to some firm object. In this way* the animal pulls itself 



calcareous spine 



epithelium of the body 
cavity ^ 



mesentery — 
pyloric caecum 



respiratory caeca 
v 



lambulacral ossicle.' 
ectodermal covering 



pedicellaria- 




— ampulla 



'tube foot 



. radial 'canal / 
radial blood-vessel 



Fig. 19. — Semi-diagrammatic figure of cross-section of the ray of a starfish, 

Asterias sp. 

along by successive " steps.' This entire system, called 
the water-vascular system, is characteristic of the branch 
Echinodermata. In addition to the fluid in the water- 
vascular system there is yet another body-fluid, the peri- 
visceral fluid, which bathes all of the tissues and fills the 
body-cavity. 

Technical Note. — Take a drop of the perivisceral fluid from a 
living starfish and examine under high power of microscope, noting 
the amoeboid cells it contains. 

The perivisceral fluid is aerated through outpocketings 
of the thin body-wall which extend outward between the 
calcareous plates of the body. These outpocketings have 



BRANCH ECHINODERMATA: STARFISHES, ETC. 113 

already been mentioned as the respiratory caeca (see 
p. 109). Surrounding the stone canal is a thin mem- 
branous tube, and within it and by the side of the stone 
canal is a soft tubular sac. The function of these organs 
is not certainly known. 

Work out the nervous system; note, as its principal 
parts, a nerve-ring about the mouth, and nerves running 
from this ring beneath the radial canals along each arm. 

Life-history and habits. — The starfishes are all marine 
forms. They hatch from eggs, and in their early stages 
are very different in appearance from the adults. At first 
they are bilaterally symmetrical, their radial symmetry 
being acquired later. Thousands of eggs and sperm-cells 
are extruded into the sea-water, where fertilization and 
development take place. The young swim freely in the 
open sea, feeding on microscopic organisms, and then 
undergo very radical changes in the course of their 
development. The adults are for the most part carniv- 
orous, feeding on crabs, snails, and the like. The live 
prey is surrounded by the extruded stomach which secretes 
fluids that kill it, after which the soft parts are digested. 
(See general account of the life-history of Echinoderms 
on p. 1 19..) . 

THE SEA-URCHIN (StrongyZocentrottts sp.) 

External Structure. — Technical Note.— If fresh or alco- 
holic specimens or even the dry "tests" of the sea-urchin (tig-. 20) 
are to be had, the general characteristics of the external structure 
can be made out. 

How does the external surface of the sea-urchin differ 
from that of the starfish ? Can you find the very long 
tube-feet ? Where is the mouth-opening ? With what is 
it surrounded ? Each tooth is enclosed in a calcareous 
framework. The whole structure is known as "Aristotle' s 
lantern. ' ' 



114 ELEMENTARY ZOOLOGY 

Technical Note. — Remove the spines from the underlying 
shell or test (fig. 21) and wash the test until perfectly clean, or place 
in a solution of lye for a short time and then wash. 

Note the characteristic radial symmetry of the shell or 
test. Note on the aboral aspect, diverging from the 
medial anal aperture, five double rows of pores. What 
are these for ? Each of the five divisions set with pores 



Fig. 20. — A sea-urchin, Strongylocenlrotus franciscaniis. (From specimen 
from Bay of Monterey, Calif.) 

is called an ambidacral area, while the intervening seg- 
ments which support the long spines are called the 
inter ambulacral areas. Note on the aboral surface, sur- 
rounding the median-placed anal aperture, a series of 
small plates. Those which are located in the interambu- 
lacral areas are the genital plates. Through these plates 
the ducts from the reproductive organs open by small 
pores. Note a very much enlarged plate with a striated 
appearance. This is the madreporite, which, as in the 
starfish, is the external opening of the stone canal and 
water-vascular system. Note the small ocular plate at 
the tip of each ambulacral area. The ocular plates con- 



BRANCH ECHINODERMATA : STARFISHES, ETC. 115 

tain small pigment-cells and communicate with the 
nervous system. 

From a general inspection of the sea-urchin's shell the 
Echinoderm characteristics, namely, radial symmetry and 
the presence of the water-vascular system, are readily 
seen. While at first glance there is apparent little 
similarity between the starfish and sea-urchin, neverthe- 
less careful examination shows that the two animals -are 







Fig. 21. — "Test" of sea-urchin, Strongylocentrotus franciscanus, with 
spines removed. (From specimen.) 

alike in their fundamental structure. Both are radially 
symmetrical. The position of the anal opening makes 
both starfish and sea-urchin slightly asymmetrical. In 
both the madreporite and anus are on the aboral side, 
while the mouth is centrally located on the oral side. 
In the starfish we noted five ambulacral areas, one on the 
under side of each arm ; similarly we find five in the sea- 
urchin. In both cases also we find the ocular spots at 
the tips of the ambulacral areas. The genital apertures 
are situated interradially in the starfish. In the sea- 
urchin they are similarly placed. The dissimilarity 
between the two forms is largely due to the very much 
developed outer spines and the dorso-ventral thickening 
of the disk in the sea-urchin. The starfish is carnivorous, 
while the sea-urchin lives on vegetable matter consisting 



n6 ELEMENTARY ZOOLOGY 

for the most part of green algae and the red sea-weeds. 
Correlated with this difference in food-habits there are 
certain differences in the structure of the internal organs. 
For example, the alimentary canal in the sea-urchin winds 
in about two and one-half turns within the body-cavity 
before it reaches the anus. 



OTHER STARFISHES, SEA-URCHINS, SEA-CUCUMBERS, 

ETC. 

Without exception all the Echinoderms, under which 
term are included the starfishes, sea-urchins, brittle-stars, 
feather-stars, and sea-cucumbers, live in the ocean. Some 
of them, the starfishes and sea-urchins, are among the 
most common and familiar animals of the seashore. Most 
of them are not fixed, but can move about freely, though 
slowly. Some of the feather-stars are fixed, as the 
sponges and polyps are. 

Shape and organization of body. — The body-shape of 
the Echinoderm varies from the flat, rayed body of the 
starfish to the thick, flattened egg-shape of the sea-urchin, 
the melon-like sac of the sea-cucumber and the delicate 
many-branched head of the sea-lily sometimes borne on 
a slender stalk. But in all these shapes can be seen more 
or less plainly a symmetrical, radiate arrangement of the 
parts of the body. The Echinoderm body has a central 
portion from which radiate separate arm or branch-like 
parts, as in the starfishes and sea-lilies, or about which 
are arranged radiately the internal body-parts, although 
the external appearance may at first sight give no plain 
indication of the radiate arrangement. This is the case 
with the sea-urchins and sea-cucumbers, yet, as has been 
seen in the sea-urchin, the radiate arrangement can be 
readily perceived by closer examination of the surface of 
the egg- or sac-like body. The radiating parts of the 



BRANCH ECHINODERMATA: STARFISHES, ETC. 117 

body are usually five. In the body of an Echinoderm 
can be usually recognized an upper or dorsal surface and 
a lower or ventral surface. The mouth is usually situated 
on the ventral side and the anal opening on the dorsal. 
Echinoderms agree also in having a calcareous outer 
skeleton or body-wall usually in the condition of definitely- 
shaped plates or spicules fitted either movably or rigidly 
together. This outer body-wall or exoskeleton may bear 
many tubercles or spines. These spines are sometimes 
movable. The body-wall of the sea-urchin shows very 
well the exoskeleton composed of plates on which are 
borne movable strong spines. 

Structure and organs. — As has been learned from the 
dissection of the starfish, the Echinoderms have well- 
developed systems of organs. The body-structure in its 
complex organization presents a marked advance beyond 
the structural condition of the polyps and jellyfishes. 
There is a well-organized digestive system with mouth, 
alimentary canal, and anal opening. The alimentary 
canal is either a simple spiral or coiled tube, or it is a tube 
in which can be recognized different parts, namely, 
oesophagus, stomach, intestine, caeca, and special glands 
secreting digestive fluids. This alimentary canal is not, 
as in the polyps, simply the body-cavity, but it is an in- 
closed tubular cavity lying within the general body-cavity. 
At the mouth-opening there is in some Echinoderms, 
notably the sea-urchins, a strong masticating apparatus 
consisting of five pointed teeth which are arranged in a 
circle about the opening. The nervous system consists 
of a central ring around the oesophagus or mouth, from 
which branches extend into the radiately arranged arms 
or regions of the body. There is no brain as in the 
higher animals, but the central nerve-ring is composed of 
both nerve-cells and nerve-fibres as in the nerve-centres 
of higher forms. Of organs of special sense there are 



1 1 8 ELEMENTARY ZOOLOGY 

special tactile or touch organs in all the Echinoderms, 
and the starfishes have very simply composed eyes or 
eye-like organs at the tips of the rays. 

While some of the Echinoderms breathe simply through 
the outer body-wall, taking up by osmosis the air mixed 
with the water, some of them have special^ though very 
simple, gill-like respiratory organs. These organs con- 
sist of small membranous sacs which are either pushed 
out from the body into the water, or lie in cavities in the 
body to which the water has access. There is also a dis- 
tinct circulatory system, but the " blood' which is 
carried by these organs and which fills the body-cavity 
consists mainly of sea-water, although containing a 
number of amoeboid corpuscles containing a brown pig- 
ment. There is no organ really corresponding to the 
heart of the higher animals. There are distinct organs 
for the production of the germ or reproductive cells. The 
sexes are distinct (except in a few species), each individual 
producing only sperm-cells or egg-cells, but the organs 
or glands which produce the germ-cells are very much 
alike in both sexes. There is no apparent difference 
between male and female Echinoderms except in the 
character or rather in the product of the germ-cell pro- 
ducing organs. A few species are exceptions, certain 
starfishes showing a difference in color between males and 
females. 

As all of the Echinoderms except some of the feather- 
stars can move about, they have organs of locomotion, 
and well-defined muscles for the movement of the loco- 
motory organs. The external organs of locomotion, the 
tube-feet (in the sea-urchins the dermal spines aid also in 
locomotion), are parts of a peculiar system of organs 
characteristic of the Echinoderms, called the ambulacral 
or the water-vascular system. This system is composed 
of a series of radial tubular vessels which rise from a cen- 



BRANCH ECHINODERMA TA : S TARFISHES, ETC. 119 

tral circular or ring vessel and which give off branches to 
each of the tube-feet. The water from the outside enters 
the ambulacral system through a special opening, the 
madreporic opening, and flowing to the tube-feet helps 
extend them. The tube-feet usually have a tiny sucking 
disk at the tip, and by means of them the Echinoderm 
can cling very firmly to rocks. 

Development and life-history. — Differing from the 
sponges and the polyps and jellyfishes, the reproduction 
of the Echinoderms is always sexual ; young or new indi- 
viduals are never produced by budding, or in any other 
asexual way. The new individual is always developed 
from an egg produced by a female and fertilized by the 
sperm of a male. The eggs are usually red or yellow, 
are very small (about ^ in. in diameter in certain 
starfishes), and are fertilized by the sperm-cells of the 
males after leaving the body of the female. That is, both 
sperm-cells and unfertilized egg-cells are poured out into 
the water by the adults, and the motile sperm-cells in 
some way find and fertilize the egg-cells. 

From the egg there hatches a tiny larva which does 
not at all resemble the parent starfish or sea-urchin. It 
is an active free-swimming creature, more or less ellip- 
soidal in shape and provided with cilia for swimming. 
Soon its body changes form and assumes a very curious 
shape with prominent projections. The larvae of the 
various kinds of Echinoderms, as the starfishes, sea- 
urchins, sea-cucumbers, etc., are of different characteristic 
shapes. The naturalists who first discovered these odd 
little animals did not associate them in their minds with 
the very differently shaped starfishes and sea-urchins, but 
believed them new kinds of fully developed marine 
animals, and gave them names. Thus the larvae of the 
starfishes were called Bipinnaria, the larvae of the sea- 
urchins Pluteus, and so on. These names are still used 



120 ELEMENTARY ZOOLOGY 

to designate the larvae, but with the knowledge that 
Bipinnaria are simply young starfishes, and that a Pluteus 
is simply a young sea-urchin. From these larval stages 
the adult or fully developed starfish or sea-urchin develops 
by very great changes or metamorphoses. The Echino- 
derms have in their life-history a metamorphosis as strik- 
ing as the butterflies and moths, which are crawling 
worm-like caterpillars in their young or larval condition. 

Most of the Echinoderms have the power of regenerat- 
ing lost parts. That is, if a starfish loses an arm (ray) 
through accident, a new ray will grow out to replace the 
old. And this power of regeneration extends so far in 
the case of some starfishes that if very badly mutilated 
they can practically regenerate the whole body. This 
amounts to a kind of asexual reproduction. Some 
species, too, have the peculiar habit of self-mutilation. 
4 4 Many brittle stars and some starfishes when removed 
from the water, or when molested in any way, break off 
portions of their arms piece by piece, until, it may be, 
the whole of them are thrown off to the very bases, 
leaving the central disc entirely bereft of arms. A central 
disc thus partly or completely deprived of its arms is 
capable in many cases of developing a new set; and a 
separated arm is capable in many cases of developing a 
new disc and a completed series of arms.' In some of 
the sea-cucumbers "it is the internal organs, or rather 
portions of them, that are capable of being thrown off and 
replaced, the oesophagus . . .or the entire alimentary 
canal, being ejected from the body by strong contrac- 
tions of the muscular fibres of the body-wall, and in 
some cases, at least, afterwards becoming completely 
renewed." 

Classification. — The Echinodermata are divided into 
five classes, viz., the Asteroidea or starfishes, "free 
Echinoderms with star-shaped or pentagonal body, in 



BRANCH ECH1N0DERMATA : STARFISHES, ETC. 121 

which a central disc and usually five arms are more or 
less readily distinguishable, the arms being hollow and 
each containing a prolongation of the body-cavity and 
contained organs"; the Ophiuroidea, or brittle-stars, 
"star-shaped free Echinoderms, with a central disc and 
five arms, which are more sharply marked off from the 
disc than in the Asteroidea and which contain no spacious 
prolongations of the body-cavity"; the Echinoidea, or 
sea-urchins, "free Echinoderms with globular, heart- 
shaped, or disc-shaped body enclosed in a shell or corona 
of close-fitting, firmly united calcareous plates"; the 
Holothuroidea, or sea-cucumbers, "free Echinoderms 
with elongated cylindrical or five-sided body, . . . with a 
circlet of large oral tentacles " ; and the Crinoidea, or 
feather-stars, "temporarily or permanently stalked Echi- 
noderms with star-shaped body, consisting of a central disc, 
and a series of five bifurcate or more completely branched 
arms, bordered with pinnules." 

Starfishes (Asteroidea). — The starfishes feed on other 
marine animals, especially shell-fish and crabs. They 
are also reputed to destroy young fish. By means of their 
sucking-tubes, or tube-feet with sucker tips, they can 
seize and hold their prey firmly. They do much injury 
to oyster-beds by attacking and devouring the oysters. 
When attacking prey too large to be taken into the mouth 
the starfish everts its stomach over the prey and devours 
it. The stomach is afterward drawn back into the body- 
cavity by special muscles. 

Starfishes vary much in size, color and general appear- 
ance, although all are readily recognizable as starfishes 
(fig. 22). The number of arms or rays varies from five 
to thirty or more in different species; some have the 
interradial spaces filled out nearly to the tips of the rays, 
making the animal simply a pentagonal disc. In size 
starfishes vary from a fraction of an inch in diameter to 



122 



ELEMENTARY ZOOLOGY 



three feet; in color they are yellow or red or brown or 
purple. 

Brittle-stars (Ophiuroidea) . — The brittle-stars, or ser- 



"t~ 








Fig. 22. — A group of Echinoderms; the 
upper one, a starfish, Asterina mineata, 
the one at the right a starfish, Asterias 
ocracia, at the left a brittlestar, spe- 
cies unknown, and at bottom two sea- 
urchins, Strorigylocentrotus franciscanus. 
(From living specimens in a tide-pool on 
the Bay of Monterey, California.) 



pent-stars (fig. 22) as 
they are also called, 
resemble the starfishes 
in external appearance, 
that is, they are flat and 
composed of a central 
disc with radiating arms 
(always five in number, 
although each arm 
may be several times 



branched). The central 
disc is always sharply distinguished from the arms, and 
the arms are usually slender and more or less cylin- 



BRANCH ECHINODERMATA: STARFISHES, ETC, 123 

drical. The distinguishing difference between the brittle- 
stars and the starfishes is that the body-cavity and the 
stomach which extend out into the arms in the star- 
fishes are in the brittle-stars limited to the central disc, or 
to the disc and bases of the arms. The tube-feet also 
have no suckers at the tips. More than 700 species of 
brittle-stars are known. They feed on marine shell-fish, 
crabs and worms. 

Sea-urchins (Echinoidea). — The sea-urchins (figs. 20, 21 
and 22) of which more than 300 species are known, have 
no arms or rays, and they are usually not flat like the star- 
fishes but globular, with poles more or less flattened. As 
has been noted in the examination of the body-wall or 
" shell, ' ' the radiate character of the body is shown by the 
five radiating zones of tube-feet. The mouth, with its five 
strong " teeth," is on the ventral surface, and the anal 
opening and madreporic opening are on the dorsal sur- 
face. The calcareous plates (seen distinctly in a specimen 
from which the spines have been removed) which consti- 
tute the firm part of the body-wall, are more or less 
pentagonal in shape and are usually firmly united at the 
edges. The spines which are so characteristic of the 
sea-urchins vary much in size and number and firmness, 
but are present in some form on all of them. 

While most of the sea-urchins live near the shore, 
being very common in tide-pools, some live only on the 
bottom of the ocean at great depths. Their food consists 
of small marine animals and of bits of organic matter 
which they collect from the sand and debris of the ocean 
floor. Many of the sea-urchins are gregarious, living 
together in great numbers. Some have the habit of 
boring into the rocks of the shore between tide-lines. I 
have seen thousands of small beautifully colored purple 
sea-urchins lying each in a spherical pit or hole in hard 
conglomerate rock on the California coast. How they 



124 ELEMENTARY ZOOLOGY 

are enabled to bore these holes is not yet known. 
There is great variety in size and color among the sea- 
urchins. The colors are brown, olive, purple red, greenish 
blue, etc. 

A few kinds of sea-urchins have a flexible shell or test. 
The Challenger expedition dredged up from sea-bottom 
some sea-urchins, and when placed on the ship's deck 
"the test moved and shrank from touch when handled, 
and felt like a starfish.' The cake-urchins or sand- 
dollars are sea-urchins having a very flat body with short 
spines. They lie buried in the sand, and are often very 
brightly colored. Their hollow bleached tests with the 
spines all rubbed off are common on the sands of both 
the Atlantic and Pacific coasts. 

Sea-cucumbers (Holothuroidea). — The sea-cucumbers 
(fig. 23) show at first glance little resemblance to the 
other radiate animals. The body is an elongate, sub- 
cylindrical sac, resembling a thick worm or sausage or 
cucumber in shape. At one end it bears a group of 
branched tentacles which are set in a ring around the 
mouth-opening. The body-wall is muscular and leathery, 
but contains many small separated calcareous spicules. 
There are usually five longitudinal rows of tube-feet. In 
some species, however, tube feet are wholly wanting; in 
others they are scattered over the surface. 

Although there are known about five hundred species 
of sea-cucumbers many of which live along the shores, 
they are much less familiar to us than the starfishes and 
sea-urchins. They usually rest buried in the sand by day, 
feeding at night. Some of them attain a large size. A 
great orange-red species of the genus Cuciimaria, which 
is found in the Bay of Monterey, California, is three feet 
long. 

The people of some nations use sea-cucumbers as food. 
They are called ' ' trepang ' ' in the orient. The trade of 



BRANCH ECHINODERMATA : STARFISHES, ETC. 



125 



preparing the trepang is almost entirely in the hands of 
the Malays, and every year large fleets set sail from 




Fig. 23. — A sea-cucumber, Pent acta J rondos a. (After Emerton.) 

Macassar and the Philippines to the south seas to catch 
sea-cucumbers. 

Feather-stars (Crinoidea) . — The feather-stars or sea- 
lilies or crinoids (fig. 24), as they are variously called, differ 
from the other Echinoderms in having the mouth on the 
upper side of the central disc, and in the fact that all of 
the species are fixed, either permanently or for a part of 
their life, being attached to rocks on the sea-bottom by 
a longer or shorter stalk which is composed of a series of 
rings or segments. The central disc is small and the 



126 ELEMENTARY ZOOLOGY 

radiating arms are long, slender, sometimes repeatedly 
branched, and all the branches bear fine lateral projec- 
tions called pinnulae. Most of the feather-stars live in 
deep water and are thus only seen after being dredged 
up. They feed on small crab-like animals, and on the 
marine unicellular animals and plants. 




Fig, 24 A crinoid or feather-star, Pentacrinus sp. (After Brehm.) 



CHAPTER XIX 
BRANCH VERMES:- THE WORMS 

THE EARTHWORM {Lumbricus sp.). 

Technical Note. — Obtain live earthworms of large size, killing 
some in 30^ alcohol and hardening and preserving them in 80^ alco- 
hol, and bringing others alive to the laboratory. The worms may 
be found during the daytime by digging, or at night by searching 
with a lantern. They often come above ground in the daytime 
after a heavy rain. Live specimens may be kept in the laboratory 
in flower-pots filled with soil. "They may be fed on bits of raw 
meat, preferably fat, bits of onion, celery, cabbage, etc., thrown on 
the soil" 

External structure (fig. 25). — Examine the external 
structure of live and dead specimens. Which is the ventral 
and which the dorsal surface ? Which the anterior and 
which the posterior end ? Note the segmented condition 
of the body; the number of segments or somites, and their 
relative size and shape. Note absence of appendages such 
as limbs and the presence of locomotor setce (short bristles). 
How many setae are there on each segment and what is 
their disposition ? The month is covered by a dorsal 
projection called the prostomium. The anal opening is 
situated in the posterior segment of the body. The broad 
thickened ring or girdle including several segments near 

* The author recognizes the untenability of the group Vermes as a group 
co-ordinate with the other branches of the animal kingdom, and that 
"Vermes" has been discarded in modern text-hooks. But because of the 
very scant consideration whic^ can be given the various kinds of worm-like 
animals the course of the older text-books will be followed, and all of the 
worm-like animals, as far as referred to in this book, be considered under 
the group name Vermes. 

127 



128 



ELEMENTARY ZOOLOGY 



retractor and protractor 
muscles of the pharynx^ 

oesophageal pouches- 
reproductive organs = 

reproductive organs — _-_-£~~~~~, 



cerebral ganglion 



, pharynx 
oesophagus 



anus. 






fc. 



crop 

nephridium - - 

gizzard — 





X 




clitelluiri 



dorsal blood vessel-- 



-<£; 



Fig. 25. — Dissection of the earthworm, Lumbricus sp. 



BRANCH VERMES: THE WORMS 129 

the anterior end of the body is the clitellum, a glandular 
structure which secretes, the cases in which the eggs are 
laid. On the ventral surface of the fourteenth and 
fifteenth segments (in most species) are two pairs of small 
pores; two other pairs of small openings (usually difficult 
to find), one between segments 9 and 10, and one between 
segments 10 and 1 1, are present. All these are the 
external openings of the reproductive organs. 

Make drawings showing the external structure of the 
eartrnvorm. 

Examine a live specimen placed on moist paper or 
wood. Note the characteristics of its locomotion, and 
the movements of its body-parts. How do the setae aid 
in locomotion ? 

Internal structure (figs. 25, 26 and 28).— technical 

Note. — With a fine-pointed pair of scissors make a dorsal median 
incision, not too deep, behind the clitellum and cut forward as far 
as the first segment. Put the specimen into dissecting-dish, care- 
fully pin back the edges of the cut and cover with clear water or, 
better, 50? alcohol. 

Note the long body-cavity divided by the thin septa 
which have been torn away for the most part by the 
pinning process. Note the thin transparent covering of 
the body, the cuticle. Just beneath this note a less trans- 
parent layer, the epidermis, and underneath this a layer 
of muscles. The muscular layer is made up of two 
clearly recognizable sets, an outer circular layer and an 
inner longitudinal layer the fibres of which are continuous 
with the septa. 

Note, as the most conspicuous internal organ, the long 
alimentary canal, of which a number of distinct parts may 
be recognized. Most anteriorly is a muscular pJiarynx, 
which is followed by a narrow cesopliagiis, leading directly 
into the thin-walled crop; next comes the muscular 



130 ELEMENTARY ZOOLOGY 

gizzard, and next the intestine which opens externally in 
the terminal segment through the anus. The anterior end 
of the alimentary canal is more or less protrusible, while 
the posterior portion is held more firmly in place by the 
septa which act as mesenteries. Surrounding the narrow 
oesophagus are the reproductive organs, three pairs of 
large white bodies and two pairs of smaller sacs. 

Note the dorsal blood-vessel lying along the dorsal 
surface of the alimentary canal, from the anterior por- 
tion of which arise several circumcesophageal rings or 
''hearts." These hearts are contractile and serve to 
keep the blood in motion through the blood-ve.ssels (see 
later). In the most anterior of the body segments note 
the pear-shaped brain or cerebral ganglion. 

Technical Note. — Lilt carefully to right and left the repro- 
ductive organs, thus exposing the oesophagus. 

Note three pairs of bag-like structures projecting from 
the oesophagus. The front pair is the oesophageal pouches; 
the next two pairs are the oesophageal or calciferous 
glands. They communicate with the alimentary canal, 
and their secretion is a milky calcareous fluid. 

Make a drawing that will show all the parts so far 
studied. 

Technical Note. — Cut transversely through the alimentary 
canal in the region of the clitellum and carefully dissect the anterior 
portion of the canal away from the surrounding organs. 

Note the dorsal fold of the intestine, typhlosole, ex- 
tending into the lumen. This fold gives a greater surface 
for digestion, and in it are a great many hepatic or special 
digestive cells. The entire alimentary canal is lined with 
epithelium. Observe just beneath the alimentary canal 
the ventral blood-vessel, and still beneath this blood- 
vessel the ventral nerve-cord. There is a slight swelling 
on the nerve-cord in each segment of the body. These 



BRANCH VERMES: THE IVORMS 



*3* 



swellings are the ganglia. How many pairs of nerves 
are given off from each ganglion ? Observe in each seg- 
ment, posterior to the first three or four, the successive 



.dorsal blood vessel 



iyphlosole 




intestine 



„^septa 



-body wall 
/.nephridia 



nephroslome 



'T^pT 



ventral blood vessel 



ventral nerve cord 
Fig. 26. — Dissection to show alimentary canal in section and nephridia 

of earthworm. 

pairs of convoluted tubes, the ncpliridia, or organs of 
excretion. Each nephridium opens internally through a 
ciliated funnel, the ncplirostomc, within the body-cavity, 
while it opens externally by a small excretory pore 
between the setae on the ventral surface of the segment 
behind that in which the nephridium chiefly lies. The 
function of the nephridia is to carry off waste matter 
from the fluid which fills the body-cavity. 

Trace the ventral nerve-cord forward to its connection 
with the cerebral ganglion. Note the throat nerve-ring 
or cwannoesopliageal collar connecting the ventral cord 
with the brain. 

Make a drawing of the nervous system showing its 
relation to other organs. 

Life- history and habits. — The earthworm lives in soft 
moist soil which is rich in organic matter. Its food is 



I 3 2 



ELEMENTARY ZOOLOGY 



taken into the mouth mixed with dirt and sand. As this 
mixture passes through the long alimentary canal the 
organic particles are taken up and digested. As we have 
already seen, there are in each worm two sets of reproduc- 
tive glands, namely, male and female organs. Each 
earthworm produces both egg-cells and sperm-cells, but 



nephridium 



hepatic cells 



dorsal blood vessel 
i 

/ 

/ longitudinal muscle 
^circular muscle fibres 
epidermis 
cuticle 




typhlosole 
~setae 



I \ nerve* cord\ 
nephndipore j nephrostome \ 

* ventral vessel 



body cavity 



Fig. 28. — Cross-section of earthworm. 



the sperm-cells of one worm are not used to fertilize the 
eggs of the individual producing them. When the eggs 
are ready to be discharged from the body, the clitellum 
becomes very much swollen and its glands begin an active 
secretion which hardens and forms a collar-like structure 
about the body of the worm. As this collar moves 
forward toward the anterior end of the body it collects the 
eggs and also the sperm-cells previously received from 



BRANCH VERMES: THE WORMS 133 

another worm, and finally slips off the head end of the 
animal. The entire structure with the contained e^ps 
and sperm-cells as it passes off from the body becomes 
closed at both ends, thus forming a horny capsule which 
lies in the earth until the young worms emerge. Only a 
part of the eggs develop in each capsule, the rest being 
used as food for the growing young. The young earth- 
worms, though of very small size, are fully formed before 
they leave the egg-capsule. Earthworms are more or less 
gregarious, large numbers often being found together. 

For an interesting account of the habits of earthworms 
see Darwin's "The Formation of Vegetable Mold." 



OTHER WORMS. 

The branch Vermes comprises so large a number of 
kinds of animals presenting such great differences in struc- 
ture and habit that it is impossible to give a brief state- 
ment in general or summary terms of their external 
body-characters, of the structural and functional condition 
of their various organs and systems of organs, and of the 
course of their development and life-history as has been 
done for the preceding branches. Many zoologists, 
indeed, do not include all the worms or worm-like animals 
in one branch, but consider them to form several distinct 
branches. 

In certain very general characters all of the animals 
which compose the branch Vermes do agree. All, .or 
nearly all, have an elongate body which is bilaterally 
symmetrical, that is, which could be cut by a median 
longitudinal cutting in two similar halves. In most of 
them also the body is composed of a number of successive 
segments or somites which are more or less alike. . This 
kind of segmented or articulated body is also possessed by 



*3l 



ELEMENTARY ZOOLOGY 



the insects and crabs. Almost all of the worms have the 
power of locomotion ; usually that of crawling. For 
this crawling they do not have legs composed of separate 
segments or joints as do the higher articulated animals, 




Fig. 29. — A group of marine worms; at the left a gephyrean, Dendrostomun, 
cronjhelmi, the upper right-hand one a nereid, Nereis sp., the lower 
right-hand one, Polynoe brevisetosa. 'From 
tide-pool on the Bay of Monterey, California.) 



living specimens in a 



the crabs and insects, but either have fleshy unjointed 
legs, or various kinds of bristles or spines, or suckers, or 
even no external organs of locomotion at all. As regards 
their internal structure they have well-organized systems 
of organs, which show great variety in character and 
degree of complexity. The special sense-organs are 
usually of simple character and low degree of functional 
development. Reproduction occurs both sexually and 
asexually; in some species the sexes are distinct, while 
in others both sperm-cells and egg-cells are produced by 
the same individual. Asexual reproduction is by budding 
or by a kind of simple division or fission. The worms 
live either in salt or fresh water, or in moist, muddy or 
slimy places or as parasites in the bodies of other animals 
or in plants. While most worms feed on animal sub- 



BRANCH VERMES: THE WORMS 1 35 

stance either living or dead, some feed on living or 
decaying plant matter. 

Classification. — There is great lack of agreement 
among zoologists in the matter of the classification of the 
worms. Not only are the various groups which by some 
are called classes held by others to be distinct branches, 
co-ordinate in rank with the Echinodermata, Coelenterata, 
etc., but the limits of these groups are also constantly 
called in question. It will require a great deal better 
knowledge of the structure and life-history of these diverse 
animals before the matter of their classification is satisfac- 
torily settled. We shall consider briefly four of the 
various groups (which we may consider as classes) which 
include worms either specially familiar to us or of special 
interest or importance. One or two examples of each 
group (the groups being selected primarily because of the 
examples) will be described in some detail. By this 
means we may get an idea of the extremely diverse char- 
acter of the animals which are included in the heteroge- 
neous branch Vermes. 

Earthworms and leeches (Oligochaetae; . — The various 
species of earthworms, an example of which has been 
studied, are found in all parts of the world; they occur in 
Siberia and south to the Kerguelen Islands. They are 
absent from desert or arid regions, and some can live 
indifferently either in soil or in water. Some near allies 
ol the earthworms are aquatic, living in fresh or brackish 
water, some in salt water near the shore. In size earth- 
worms vary from I mm. (V T in.) to 2 metres {2\ yds.) in 
length. All show the distinct segmentation of the body 
noticeable in the common earthworm already studied. 

The leeches, some of which are familiar animals, are 
closely related to the earthworms, although at first glance 
the similarity in structure is not very noticeable. 



I3 6 ELEMENTARY ZOOLOGY 

Technical Note. — Some common water-leeches, alive or pre- 
served in alcohol, should be examined by the class. The animals 
are not unfamiliar to boys who "go in swimming" in the small 
streams of the country. The body of a leech should be examined 
carefully, and drawings of it showing the external structural charac- 
ters should be made. 

The body of a leech is flattened dorso-ventrally, instead 
of being cylindrical as in the earthworm, and tapers at 
both ends. In the live animal the body can be greatly 
elongated and narrowed or much shortened and broad- 
ened. It is composed of many segments (not as many 
as there are cross-lines however; each segment is trans- 
versely annulated), and bears at each end on the ventral 
surface a sucker, the one at the posterior end being the 
larger. These suckers enable the leech to cling firmly 
to other animals. The mouth is at the front end of the 
body on the ventral surface and is provided with sharp 
jaw T s. Leeches live mostly on the blood of other animals 
which they suck from the body. The common leech 
" fastens itself upon its victim by means of its suckers, 
then cuts the skin, fastens its oral sucker over the wound 
and pumps away until it has completely gorged itself with 
blood, distending enormously its elastic body, when it 
loosens its hold and drops off. ' Its biting and sucking 
cause very little pain, and in olden days physicians used 
the leeches when they wanted to " bleed " a person. A 
common European species of leech much used for this 
purpose is known as the ''medicinal leech.' All 
leeches are hermaphroditic, that is, the sexes are not dis- 
tinct, but each individual produces both sperm-cells and 
egg-cells. . Most of the leeches lay their eggs in small 
packets or cocoons. This cocoon is dropped in soil on the 
banks of a pond or stream so that the young may have a 
moist but not too wet environment. The young issue 
from the eggs in four or five weeks, but they grow very 



BRANCH VERMES: THE WORMS 1 37 

slowly and it is several years before they attain their full 
size. Leeches are long-lived animals, some being said 
to live for twenty years. 

Flatworms (Platyhelminthes). — Technical Note.— 

Collect some live fresh-water planarians (see fig. 30), which are to be 
found on the muddy bottom of most fresh-water ponds, and examine 
them while alive in watch-glasses of water. Make drawings show- 
ing the external appearance, and as much of the internal anatomy 
as can be seen. The branching alimentary canal can be seen in 
more or less detail, and with higher power of the microscope parts 
of the nervous system can be seen also. Have also a tapeworm 
preserved in alcohol or formalin to show the very flat and many- 
segmented body. 

The flatworms include a large number of forms which 
vary much in shape and habits. They are all, however, 





Fig. 30. — A fresh water planarian, Planaria sp. (From a living specimen.) 

characteristically flat; in some this condition is very 
marked. Some are active free-living animals, as the 
planarians (figs. 30 and 31), while many live as parasites 
in the alimentary canal of other animals, as do the sheep- 
fluke and the tapeworms. 

The fresh-water planarians (fig. 30), which live com- 
monly in the mud of the bottom of ponds, are small, 
being less than half an inch long. They are very thin 
and rather broad, tapering from in front backwards. On 
the upper surface near the front they have a pair of eyes ; 
the mouth is on the under surface a little behind the 
middle of the body. The alimentary canal is composed 
of three main branches, each with numerous small side 
branches. One main branch runs forward from the 
mouth, and the other two run backwards, one on each 
side of the body. There is no anal opening, and the 



138 ELEMENTARY ZOOLOGY 

alimentary canal thus forms a system of fine branches 
closed at the tips, and extending all through the body. 
The nervous system is composed of a ganglion or brain 
in the front end of the body from which two main branches 
extend back throughout its whole length. From these 
main longitudinal branches arise many fine lateral 
branches. 

Of the parasitic flatworms the tapeworms are the best 
known. There are numerous species of them, all of 




Fig. 31. — A marine planarian, Leptoplana calif ornica. (From a living 

specimen.) 

which live in the bodies of vertebrate animals. In the 
adult or fully developed stage the tapeworms live in the 
alimentary canal, holding on to its inner surface by hook- 
like clinging organs and being nourished by the already 
digested food by which they are bathed. In the young 
or larval stage tapeworms live in other parts of the body 
of the host, and usually, indeed, in other hosts not of the 
same species as the host of the adult worm. 



BRANCH VERMES: THE IV G RMS 139 

The common tapeworm of man, T tenia solium (there 
are several other species of Tmiia which infest 
man, but solium is the common one), may serve as an 
example of the group. In the adult condition its body, 
which is found attached to the inner wall of the intestine, 
is like a long narrow ribbon : it may be two or three 
metres long. It is attached by one end, the head, which 
is very small and provided with a score of fine hooks. 
Behind the head the thin ribbon-like body grows wider. 
The body is composed of many (about 850) joints called 
proglottids. There is no mouth or alimentary canal, the 
liquid food being simply taken in through the skin. Each 
proglottid produces both sperm-cells and egg-cells ; one 
by one these proglottids or joints with their supply of 
fertilized eggs break off and pass from the alimentary 
canal with the excreta. If now one of these escaped 
proglottids or the eggs from it are eaten by a pig, the 
embryos issue from the eggs in the alimentary canal of 
the pig, bore through the walls of the canal and lodge in 
the muscles. Here they increase greatly in size and 
develop into a sort of rounded sac filled with liquid. If 
the flesh of the pig be eaten by a man, without its being 
first cooked sufficiently to kill the larval sac-like tape- 
worms, these young tapeworms lodge in the alimentary 
canal of the man and develop and grow into the long 
ribbon-like many-jointed adult stage. 

The life-history of the other tapeworms which infest 
the various vertebrate animals is of this general type. 
There is almost always an alternation of hosts, the larval 
tapeworm living in a so-called intermediate host, and the 
adult in a final host. Of the domestic animals the dog 
is the most frequently attacked. At least ten different 
species of tapeworms have been found in the dog. The 
intermediate hosts of these dog tapeworms include 
rabbits, sheep, mice, etc. Some of the domestic fowl, 



140 



ELEMENTARY ZOOLOGY 



ducks, geese and chickens, for instance, are also infested 
by tapeworms, and the intermediate hosts in these cases 
are usually insects or small aquatic crustaceans like the 
familiar Cyclops. 

Roundworms (Nemathelminthes) . — Technical note.— 

Vinegar-eels from mouldy vinegar, and hair-worms from fresh- 
water pools, can usually be readily obtained. They should be 
examined, and drawings should be made of them, showing their 
shape and simple external structural character. If a specimen of 
trichinosed pork be obtained, the encysted stage of 
the Trichina, described in the following account, can 
be shown. 

The roundworms are slender, smooth, 
cylindrical worms pointed at both ends. 
They are all very long in proportion to their 
diameter, although their actual length may 
be short. Some species are of microscopic 
size; as the Trichina worm, which is about 
J^ in. long; while the guinea-worm, one of 
the worst parasites of man, may reach a 
length of six feet. Many of the round- 
worms are parasites living in the various 
organs of other animals. Some, however, 
lead an independent free life in water or in 
damp earth. 

Familiar examples of roundworms are the 
so-called vinegar-eels (Anguillnlci) (fig. 32) 
to be found in weak vinegar, and other 
species of this same genus which live in water 
or moist ground or in the tissues of plants, 
doing much injury. The hair-worms (Gor- 
dius) or horse-hair snakes, which are believed 
by some people, to be horse-hairs dropped 
into water and turned into these animals, are 
also familiar examples of roundworms. They 
are often found abundantly in little pools after a rain, and 



Fig. 32. — A 
vinegar eel, 
Anguiilula 
sp. (From 
a living 
specimen.) 



BRANCH VERMES: THE WORMS 141 

it is sometimes said that these worms come down with the 
rain. They have in reality come from the bodies of insects 
in which they pass their young or larval stages as parasites. 
The hair-worms all live as parasites during their larval 
stage, and as free independent animals in their adult stage. 
Some of them require two distinct hosts for the comple- 
tion of their larval life, living for a while in the body of 

one, and later in the body of 

I another. The first host is 

usually a kind of insect which is 

\ eaten by the second host. The 

eggs are deposited by the free 

adult female in slender strings 

twisted around the stems of 

l \ water-plants. The young hair- 

, worm on hatching sinks to the 

\l bottom of the pond, where it 

moves about hunting for a host 

/ in which to take up its abode. 

The terrible Trichina spiralis 

(fig"- 33)» which produces the 

disease called trichinosis, is 

another roundworm of which 

( much is heard. This is a very 

/' : j small worm which in its adult 

condition lives in the intestine 

^ ^ of man as well as in the pig and 

Fig. ^-Trichina spiralis, en- Qther mammals . The young, 
cysted in muscle 01 a pig. J ° 

(From specimen.) which are borne alive, burrow 

through the walls of the intes- 
tine, and are either carried by the blood, or force their 
way, all over the body, lodging usually in muscles. 
Here they form for themselves little cells or cysts in 
which they lie. The forming of these thousands of tiny 
cysts injures the muscles and causes great pain, sometimes 




142 ELEMENTARY ZOOLOGY 

death, to the host. Such infested muscle or flesh is said 
to be " trichinosed, ' : and the flesh of a trichinosed 
human subject has been estimated to contain 100,000,000 
encysted worms. To complete the development of the 
encysted and sexless Tricliince the infested flesh of the 
host must be eaten by another animal in which the worm 
can live, e.g. the flesh of man by a pig or rat, and that 
of a pig by man. In such a case the cysts are dissolved 
by the digestive juices, the worms escape, develop repro- 
ductive organs and produce young, which then migrate 
into the muscles and induce trichinosis as before. But 
however badly trichinosed a piece of pork may be, 
thorough cooking of it will kill the encysted Trichince, so 
that it may then be eaten with impunity. Some people, 
however, are accustomed to eat ham, which is simply 
smoked pork, without cooking it, and in such cases there 
is always great danger of trichinosis. 

Wheel animalcules (Rotifera). — Technical Note.- Live 
specimens of Rotifers can be found in almost any stagnant water 
Examine a drop of such water with the compound microscope, and 
find in it a few small, active, transparent creatures, larger than the 
Paramoccium and other Protozoa in the water and which have the 
appearance shown in fig. 34. They may be known by the constant 
whirling, or rather vibrating, circlet or wheel of cilia at the larger 
or head end of the body. These wheel animalcules may be studied 
alive by the class. Although usuallv darting about, the animalcules 
occasionally cease to move, when, because of their transparency, 
almost the whole of their anatomy can be made out. Their feeding 
habits can also be readily observed, and the food itself watched 
as it moves through the body. Make drawings showing as much 
of the anatomy as can be worked out. Note especially the "mas- 
tax " or gizzard-like masticating apparatus in the alimentary canal. 

The wheel animalcules (fig. 34) or Rotifers look little 
like the other worms we have studied. But they are 
nevertheless more nearly related to the worms than to 
any other branch of animals. They are all small, about \ 
mm. long, and have a compact body. They are aquatic 
and feed on smaller animals and plants or on bits of or- 



BRANCH VERMES: THE WORMS 



!43 



m / 



ganic matter which they capture by means of the currents 
produced by the vibrating cilia of the 4 k wheel. ' Small as 

they are they have a complex 
body-structure, with well-or- 
ganized systems of organs. 
For a long time, however, 
they were classed by natural- 
ists with the Protozoa on ac- 
count of their size. They are 
found all over the world, 
mostly in fresh water ; a few 
are marine. More than 700 
species of them are known. 

An interesting thing about 
the Rotifers is their remark- 
able power to withstand dry- 
ing-up. When the water in 
a pond or ditch evaporates 
some of the Rotifers do not 

Fig. 34. — A wheel animalcule. 

Rotifer sp. (From living speci- die, but simply dry up and he 

men. Stanford University.) j n the dust< shrivelled and 

apparently lifeless, yet really in a state of suspended 
animation. On being put into water they will gradually 
fill out to their full size and shape, and finally resume all 
their normal activities. In this dried-up condition Rotifers 
may persist for a long time, several years even, although 
otherwise their natural life is short, being probably of not 
over two weeks' duration. Certain other of the lower 
animals have this same power of withstanding desiccation. 



CHAPTER XX 

BRANCH ARTHROPODA: CRUSTACEANS, CEN- 
TIPEDS, INSECTS, AND SPIDERS 

The great branch Arthropoda includes a host of 
familiar animals. It contains more species than any other 
branch of the animal kingdom. To it belong the cray- 
fishes, shrimps, crabs, lobsters, water-fleas, and other ani- 
mals which compose the class Crustacea; the centipeds 
and thousand-legged worms which compose the class 
Myriapoda ; the true or six-footed insects forming the class 
Insecta, which includes nearly two-thirds of all the known 
species of animals; and the scorpions, mites, ticks, and 
spiders which constitute the class Arachnida. There is 
also a fifth class in the branch Arthropoda which includes 
a few species of animals unfamiliar to us but of great 
interest to zoologists. 

All these varied kinds of animals have a body on the 
annulate or segmented type-plan, like that shown by most 
worms, but they differ from the worms in possessing 
jointed appendages, used for locomotion or food taking. 
There is typically or racially one pair of these jointed or 
segmented appendages on each segment of the body, but 
in all of the Arthropoda some of the segments have lost 
their appendages. The body is covered by a firm cuticle 
or outer body-wall called the exoskeleton. This exo- 
skeleton serves not only to enclose and protect the soft 
parts of the body but also for the attachment of the body 

144 



BRANCH ARTHROPODA : CRUSTACEANS 145 

muscles. It may be flexible as in the sutures between 
the body-segments in most insects, or hard and rigid as 
in the sclerites of the segments. The firmness is due 
primarily, and in the insects usually solely, to a deposit in 
the cuticle of cliitin, a substance probably secreted by the 
underlying cells of the true skin, or it maybe due chiefly, 
as in the crabs, to a calcareous deposit. In such cases it 
becomes a veritable armor. The internal organs of the 
Arthropods show a more or less obvious segmentation 
corresponding with the segmentation of the body- wall. 
The alimentary canal runs longitudinally through the 
center of the body from mouth to anal opening. The 
nervous system consists of a brain lying above the 
oesophagus and a double nerve-chain running backward 
from beneath the oesophagus, along the median line of 
the ventral wall, to the posterior extremity of the body. 
This ventral nerve-chain consists of a pair of longitudinal 
commissures or cords and a series of pairs of ganglia, 
arranged segmentally. The two ganglia of each pair are 
fused more or less nearly completely to form a single 
ganglion, and the nerve-cords are partially fused, or at 
least lie close together. In addition there is a smaller 
sympathetic system composed of a few small ganglia and 
certain nerves running from them to the viscera, this sys- 
tem being connected with the main or central nervous 
system. In this group the organs of special sense reach 
for the first time a high stage of development. Com- 
pound eyes are peculiar to Arthropoda. The heart lies 
above the alimentary canal. Respiration is carried on by 
gills in the aquatic forms, and by a remarkable system of 
air-tubes or tracheae in the land forms (insects). The 
sexes are usually distinct, and reproduction is almost uni- 
versally sexual. Most of the species lay eggs. 

The Arthropods are animals of a high degree of organ- 
ization. The extremely diverse life-habits of the various 



146 ELEMENTARY ZOOLOGY 

kinds among them have led to much modification and to 
great specialization of structure. The course of develop- 
ment, too, is made very complicated by the elaborate 
metamorphosis undergone by many of the members of the 
branch. 

We shall study the Arthropoda by getting acquainted 
with a few examples of each class and thus learning the 
special class characteristics. 



Class Crustacea: Crayfishes, Crabs, Lobsters, 

Etc. 

THE CRAYFISH (Cambarus sp.) 

Structure. — The structure of the crayfish has been 
already studied (see Chapter IV and figs. 3 and 4). 

Life-history and habits. — Crayfish frequent fresh-water 
lakes, rivers, and springs in most parts of the United 
States. Many of them perish whenever the small prairie 
ponds dry up. But some burrow into the earth when the 
dry season comes. There may be noticed in meadows 
where water stands for certain seasons of the year many 
scattered holes with slight elevations of mud about them. 
These are mostly the burrows of crayfish. During the 
dry season the crayfish digs down until it reaches water, 
or at least a damp place, where it rests until wet weather 
brings it to the surface once more. One of these burrows, 
followed in digging a mining shaft, extended vertically 
down to a distance of twenty-six feet, where the crayfish 
was found tucked snugly away. 

The eggs are carried by the female on her abdominal 
appendages. Previous to the laying of the eggs the 
female rubs off all foreign matter from the appendages, 
thus preparing them for the reception of the eggs. This 
cleaning is done with the fifth pair of legs. When the 



BRANCH ARTHROPODS : CRUSTACEANS 147 

eggs are ready to be laid, which is during the last of 
March or in April in the Central States, a sticky secretion 
passes out of the openings at the base of the walking legs 
and smears the pleopods of the abdomen. The eggs as 
they .pass out are fertilized and caught on the pleopods, 
where they remain attached in clusters. After some 
weeks the young crayfishes issue from the eggs. In 
general appearance they are not very unlike the adults. 
They grow very rapidly at this stage. As the animal is 
enclosed in a hard shell, growth can only take place 
during the period just following the molt, for the crayfish 
casts its skin periodically, and it is while the new shell is 
forming that the animal does its growing. The crayfish 
when it molts casts not only the exoskeleton, but also the 
lining of part of the alimentary canal. After the females 
have hatched their young many die in the shallow pools, 
in which places the dried-up skeletons are noticeable 
during the summer months. 

OTHER CRUSTACEANS. 

Most of the crustaceans live in water, a few being found 
in damp soil or in other moist places. Some are fresh- 
water animals and some marine. They vary in size from 
the tiny water-fleas, a millimeter long, to crabs two feet 
across the shell or sixteen feet from tip to tip of legs. 
They present great differences in form and general ap- 
pearance of body, being adapted for various conditions 
of life. Some crustaceans live as parasites on other 
animals, in some cases on other crustaceans. Such 
parasitic species have the body much modified and are 
hardly to be recognized as members of the class. 

Body form and structure. — In structural character and 
body organization the Crustaceans show, of course, the 
general characteristics already attributed to the Arthro- 
poda, the branch to which they belong. The character- 



148 ELEMENTARY ZOOLOGY 

istics which distinguish them from other Arthropods are 
the possession of gills for respiration (some insects have 
gills, but of a very different kind as will be seen later), 
and the bi-ramose condition of the body appendages, each 
appendage (excepting the antennules) consisting of a 
single basal segment from which arise two branches made 
up of one or more segments. Of the form of the crus- 
tacean body few generalizations can be made. 

"There is no [other] class in the animal kingdom 
which presents so wide a range of organization as the 
Crustacea, or in which the deviations in structure from the 
4 type form ' are so striking and so interesting from their 
obvious adaptation to the mode of life. ' For this reason 
no attempt will be made to discuss in general terms the 
form of ther crustacean body, but brief accounts will be 
given of a few of the more familiar kinds of Crustacea 
which will serve to illustrate this remarkable diversity of 
body form. 

Similarly impossible is it also to give a general account 
of the development of the crustaceans. The sexes are 
distinct in most Crustacea, and there is often great differ- 
ence in form between the male and female. A certain 
amount of metamorphosis takes place in the development 
of all crustaceans; that is, the young when hatched from 
the egg differs, often decidedly, in appearance and structure 
from the parent, and in the course of its post-embryonic 
development undergoes more or less striking change 
or metamorphosis. This metamorphosis is often very 
marked. 

Water-fleas (Cyclops). — Technical Note.— The water- 
fleas are common in the water of ponds or of slow streams ; they 
may often be found in the school aquarium. They are, though 
small (about 1 mm. long), readily seen with the unaided eye ; they 
are white, rather elongate, and have a rapid jerky movement. Ex- 
amine specimens alive in water in a watch glass. Note the "split 
pear " shape, broadest near the front, tapering posteriorly, flat be- 



BRANCH ARTHROPODS : CRUSTACEANS 



49 



neath, convex above; note the forked stylets at tip of abdomen ; also 
the two pairs of antennae, the single median eye, the mandibles, two 
pairs of maxillae, and five pairs of legs (last pair very small). There 
are no gills. Some of the specimens, females, may have attached to 
the first abdominal segment on either side an egg sac. Make 
drawings showing all these structural details. Watch the Cyclops 
capturing and feeding on Paramoscuim or other small animals. 

The water-fleas {Cyclops) (fig. 35) are among the 
smallest of the Crustacea. They are extremely abundant, 







Fig. 35. — A water- flea, Cyclops sp. Female with egg-masses. 
(From living specimen.] 

having great power of multiplication. u An old Cyclops 
may produce forty or fifty eggs at once, and may give 
birth to eight or ten broods of children living five to six 



350 ELEMENTARY ZOOLOGY 

months. As the young begin to reproduce at an early 
age, the rate of multiplication is astonishing. The 
descendants of one Cyclops may number in one year 
nearly 4,500,000,000, or more than three times the total 
population of the earth, provided that all the young reach 
maturity and produce the full number of offspring. ' : The 
Cyclops feed on smaller aquatic animals such as Protozoa, 
Rotifera, etc. They in turn serve as food for fishes; and 
because of their immense numbers and occurrence in all 
except the swiftest fresh waters iK they form the main food 
of most of our fresh-water fishes while young. ' Many 
aquatic insect larvae feed almost exclusively on them. 

Related to the Cyclops are a host of other kinds of 
minute Crustaceans. Among these the so-called fish-lice 
are specially interesting because of their parasitic habits 
and greatly modified and degenerate structure. There 
are many kinds of these parasitic crustaceans infesting 
fishes, whales, molluscs, and worms. " As on land almost 
every species of bird or mammal has its own parasitic 
insects, so in the water almost every species of fish or 
larger invertebrate has its parasitic crustaceans.' Some 
of the most common of these parasites attach themselves 
to the gills of fishes. Here they cling, sucking the blood 
or animal juices from the host. In form of body they do 
not at all resemble other Crustaceans, but are strangely 
misshapen. They are often worm-like, or sac-like, with- 
out legs or other locomotory appendages. As with other 
parasites (see Chapter XXX) an inactive dependent life 
results in the atrophy and loss by degeneration of the 
body-parts concerned with locomotion and orientation. 

Wood lice (Isopoda). — Technical Note. — Specimens of 
wood lice, pill bugs, or damp bugs, as they are variously called, may be 
readily found in concealed moist places, as under stones or boards on 
damp soil. They are often common in houses, near drains or in dark, 
damp places. Examine some live wood lice, and some dead speci- 
mens (killed by chloroform or in an insect-killing bottle). 



BRANCH ARTHROPODA : CRUSTACEANS 151 

Note the division of the body into the head, thorax, and abdomen ; 
find the eyes, the antennas and the mouthparts (mandibles and maxilla? 
are usually pressed closely together). All the locomotory append- 
ages are adapted for walking or running, not swimming. Note the 
number of pairs of legs ; the structure of a leg ; find gills and gill- 
covers. Some females may be found with eggs on the under side 
of the thorax near the bases of the legs, the eggs being covered by 
thin membranous plates. Make drawings showing the general 
form and character of body and details of legs, gills, etc. Compare 
with the crayfish and Cyclops. 

The wood-lice (fig. 36) are among the few Crustacea 
which have a wholly terrestrial life. They run about 

quickly and feed chiefly on decaying 
vegetable matter. They are night 
scavengers. They have the body 
oval and convex above, rather pur- 
plish or grayish brown, and smooth. 
Although they do not live in the 
water they breathe partly at least by 
means of gills (though they may 
breathe partly through the skin). 
It is therefore necessary for them to 

live in a damp atmosphere so that the 
Fig. 36. — A damp bug, . n , i_ 1 1 

Isopod, species not de- g lH membranes may be kept damp. 
termined. (From speci- if no t kept moist they could not 

men.) . 

serve as osmotic membranes. 
Lobsters, Shrimps and Crabs (Decapoda). — Technical 

Note. — Teachers living near the sea-shore can get specimens of 
live and dead lobsters, shrimps, and crabs in the markets. Schools 
in the interior should have a few preserved specimens for examina- 
tion. These specimens should be compared with the crayfish ; 
although differences in shape of body are evident, the character 
and arrangement of body parts will be found to be very similar. 

The largest and most familiar Crustaceans, as the cray- 
fishes, lobsters, shrimps, prawns and crabs, all belong 
to the order Decapoda, or ten-legged Crustacea. The 
members of this order have, including the large claws, 
ten walking feet; they all have eyes on movable stalks, 




152 ELEMENTARY ZOOLOGY 

and the front portion of the body is covered by a horny 
fold of the body-wall called the carapace. 

The lobsters are large ocean-inhabiting crustaceans 
which are very like the fresh-water crayfish in all struc- 
tural characters. They live on the rocky or sandy ocean- 
bottom at shallow depths. They feed largely on decaying 
animal matter. They are caught in great numbers in 
so-called " lobster pots, " a kind of wooden trap baited 
with refuse. "The number thus taken upon the shores 
of New England and Canada amounts to between twenty 
and thirty million annually. " Live lobsters are brownish 
or greenish with bluish mottling; they turn red when 
boiled. A single female will lay several thousand eggs. 
The eggs are greenish and are carried about by the mother 
until the young hatch. The young are free-swimming 
larvae, until they reach a length of half an inch. 

The shrimps and prawns are mostly marine, though 
some species live in fresh water. They are, like the 
lobsters, used for food. Some of the species are gregari- 
ous in habit, occurring in great " schools " of individuals. 
Like the lobsters they crawl about on the sea-bottom 
feeding on decaying animal matter. Shrimps are very 
abundant near San Francisco, where extensive "shrimp 
fishing " is done by the Chinese. 

The crabs (fig. 37) differ from the lobsters and cray- 
fishes and shrimps in having the body short and broad, 
instead of elongate. This is due to the special widening 
of the carapace and the marked shortening of the 
abdomen. The abdomen, moreover, is permanently bent 
underneath the body, so that but little of it is visible from 
the dorsal aspect. The number of abdominal legs or 
appendages is reduced. When the tide is out the rocks 
and tide-pools of the ocean shore are alive with crabs. 
They "scuttle " about noisily over the rocks, withdraw- 
ing into crevices or sinking to the bottom of the pools 



BRANCH ARTHROPODA : CRUSTACEANS 



x 53 



when disturbed. They move as readily backward or 
sidewise, " crab-fashion, as forward. They are of 
various colors and markings, often so patterned as to 




Fig. 37. — Some crabs and barnacles of the Pacific coast; the short sessile 
acorn barnacles in the upper left-hand corner belong to the genus Bal- 
anus; the stalked barnacles in the upper right-hand corner are of the 
species Pollicipes polymenus; the largest crab (upper left-hand) is 
Brachynotus nudus; the one in left-hand lower corner is a young rock- 
crab. Cancel- pro ductus; the crab in the sea-weed at the right is a kelp- 
crab, Epialtus prodnctas. while the two in snail-shelis in lower corner 
are hermit-crabs. Pagurns scwntelis. (From living specimens in a tide- 
pool on the Bay of Monterey. California.) 

harmonize very perfectly with the general color and ap- 
pearance of the rocks and sea-weeds among which they 



154 ELEMENTARY ZOOLOGY 

live. The spider-crabs are especially strange-looking crea- 
tures with unusually long and slender legs and a com- 
paratively small body-trunk. They include the Macro- 
cheira of Japan, the largest of the crustaceans. Specimens 
of this crab are known measuring twelve to sixteen feet 
from tip to tip of extended legs ; the carapace is only as 
many inches in width or length. The soft-shelled crab 
is a species common along our Atlantic coast. It is 
"soft-shelled " only at the time of molting, and has to 
be caught in the few days intervening between the shed- 
ding of the old hard shell and the hardening of the new 
body-wall. The little oyster-crabs {Pinnotheres) which 
live with the live oyster in the cavity enclosed by the 
oyster shell are well-known and interesting crabs. They 
are not parasites preying on the body of the oyster, but 
are simply messmates feeding on particles of food brought 
into the shell by the currents of water created by the 
oysters. 

Among the most interesting crabs are the hermit crabs 
(fig. 37), familiar to all who know the seashore. There 
are numerous species of these crabs, all of which have the 
habit of carrying about with them, as a protective covering 
into which to withdraw, the spiral shell of some gastropod 
mollusc. The abdomen of the crab remains always in 
the cavity of the shell ; the head and thorax and legs 
project from the opening of the shell, to be withdrawn 
into it when the animal is alarmed or at rest. The 
abdomen being always in the shell and thus protected 
loses the hard body-wall, and is soft, often curiously 
shaped and twisted to correspond to the cavity of the 
shell. It has on it no legs or appendages except a pair 
for the hindmost segment which are modified into hooks 
for holding fast to the interior of the shell. As the 
hermit crab grows it takes up its abode in larger and 
larger shells, sometimes killing and removing piece-meal 



BRANCH ARTHROPODS : CRUSTACEANS 1 5S 

the original inhabitant. Some hermit crabs always have 
attached to the shell certain kinds of sea-anemones. It 
is believed that both crab and sea-anemone derive advan- 
tage from this arrangement. The sea-anemone, which 
otherwise cannot move, is carried from place to place by 
the crab and so may get a larger supply of food, while 
the crab is protected from its enemies, the predaceous 
fishes, by the stinging threads of the sea-anemone, and 
also perhaps by the concealment of the shell its presence 
affords. This living together by two kinds of animals to 
their mutual advantage is called commensalism or sym- 
biosis (see Chapter XXXj. The hermit crabs are not true 
crabs, but are more nearly related to the crayfishes and 
shrimps than to the true broad-bodied, short-tailed crabs. 

Barnacles. — Technical Note. — Specimens of barnacles may 
be got readily from the tide rocks or from piles in a harbor. In- 
terior schools should have, if possible, specimens preserved in 
alcohol or formalin for examination. The "shells" of acorn (ses- 
sile) barnacles may often be found on oyster shells (get at restau- 
rants). 

Crustaceans which at first glance are hardly recogniz- 
able as such are the stalked or sessile barnacles (fig. 37) 
which live fixed in great numbers on the rocks between 
the tide lines, or on the piles supporting wharves, or on 
the bottom of ships or even on the body-wall of whales 
and other ocean animals. In the stalked forms the stalk 
is a flexible stem or peduncle covered with a blackish 
finely-wrinkled skin bearing at its free end the greatly 
modified body of the barnacle. This body is enclosed in 
a sort of bivalved shell or carapace formed by a fold of 
the skin and stiffened by five calcareous plates. Within 
this curious shell is the compact, rather worm-like body- 
mass, showing little or no indication of segmentation. 
The legs, of which there are usually six pairs, are much 
modified, being long, feathery, and divided nearly to the 



I5 6 ELEMENTARY ZOOLOGY 

base. These feathery feet project from the opened shell 
when the animal is undisturbed, and waving about in the 
water catch small animals which serve as the barnacle's 
food. When disturbed the barnacle withdraws its feet 
and closes tightly its strong protecting shell. The acorn- 
barnacles have no stalk, but look like a low bluntly- 
pointed pyramid, this appearance being due to the 
converging arrangement of six calcareous plates in its 
body-wall. 

The barnacles present several unusual conditions with 
regard to the internal organs. They have no heart nor 
any blood-vessels ; most of the species are hermaphroditic ; 
and there are other indications of a degenerate condition. 
This degeneration of the barnacles is due to their fixed 
life, the results of which are like those of a parasitic life. 
The young barnacles when hatched from the egg are free- 
swimming larvae as with the other Crustacea. They 
finally attach themselves and undergo the changes, some 
of them of degenerative nature, which produce the body- 
structure of the adult. It was long a belief among many 
people that the barnacle produced the barnacle goose. 
Pictures in ancient books show the young barnacle geese 
issuing from the opened shell of the barnacle. The early 
naturalists believed barnacles, on account of the shell, to 
be a kind of shell-fish or mollusc, but when their develop- 
ment was thoroughly worked out, it became evident that 
they belong to the Crustacea. 



CHAPTER XXI 

BRANCH ARTHROPODA {continued)] CLASS IN- 
SECTA: THE INSECTS 

THE EOCUST {Melanoplus sp.) 

Technical Note. — Locusts or grasshoppers are common and 
familiar insects all over the country. The genus Melanoplus in- 
cludes numerous species, one or more of which are to be found in 
almost any locality. The common red-legged locust (M. femur- 
rubrnm) of the East, the Rocky Mountain migratory locust (J/. 
spretus), of the West, the large differential (M. differ entialis) and 
two-striped (M. bivittatus) locusts of the Southwest, are especially 
common species. All the members of the genus have their hind 
wings uncolored, and the front wings marked with a longitudinal 
series of small dots more or less distinct, or with a longitudinal line. 
There is a small blunt spine or process projecting from the ventral 
aspect of the prothorax. If a species of Melanoplus cannot be 
found, any other locust may be used, although there are some slight 
variations in the external structure of the various species. Eresh 
specimens killed in a cyanide bottle (for preparing see p. 463) are 
preferable in the study of the external structure, but specimens 
preserved in alcohol will do. 

External structure (fig. 38). — Note that the body of 
the grass-hopper is composed of successive rings or seg- 
ments grouped into three regions, the head (anterior), 
thorax (median), and abdomen (posterior). In which 
region of the body are the segments most readily distin- 
guished ? Of how many segments does the head appear 
to be composed ? The thorax is composed of three 
segments of which the most anterior, to which is attached 
the front pair of legs, differs from the succeeding two, 
being freely movable and bearing a large hood- or saddle- 
shaped piece on its dorsal aspect. To the other two 
thoracic segments the second and third pair of legs are 

157 



158 



ELEMENTARY ZOOLOGY 



attached, as are also the two pairs of wings. The re- 
maining segments of the body compose the abdomen. 
Note the smooth, rather firm and horny character of 
antennm 




'"OVipOSltO't 



femur* 
tibia*' 

tarsal segments 

FlG. 38. — The red-legged locust. Melanoplus femur rubrum, to show ex- 
ternal structure. 

the body. This is due to the fact that the skin is every- 
where covered with a cuticle in which is deposited a 
horny substance called chitin. The cuticle is not uni- 
formly firm over the body. At the junction of the body 
segments in the abdomen, in the neck and between the 
segments of the legs, in fact, wherever motion is desir- 
able, the cuticle is flexible, thus making bending of the 
body-wall possible. Elsewhere, however, it is hard and 
stiff, serving not only as a protective coat or armor over 
the body, but also affording firm places for the attachment 
of muscles. 

Insects (and all other Arthropods) have no * internal 
skeleton, but, in this firm cuticle, an exoskeleton. 

Although the head is apparently a single segment, it 

* There are in many forms a few internal projections from the exterior 
cuticle which act as internal skeletal pieces. 



BRANCH ARTHROPODA ; CLASS 1NSECTA : THE INSECTS 159 

is really composed of six or seven body segments greatly 
modified and firmly fused together. Note that it bears 
a pair of large compound eyes and three much smaller 
simple eyes or ocelli. 

Technical Note. — Strip off a bit of the outer covering of a 
compound eye, mount on a glass slide and examine under the 
microscope. 

Note that, as in the crayfish, each compound eye is 
composed externally of many small hexagonal facets, the 
outer covering, the cornea, being simply the cuticular cover- 
ing of the body, in this place transparent and divided into 
small facets. Besides the eyes, the head bears also several 
movable appendages, namely the antennce, and the 
moutli-parts. Note the number, place of insertion, and 
segmented character of the antennae. These antennae are 
sense-organs and are used for feeling, smelling, and, in 
some insects, for hearing. Note that the mouth-parts 
consist of an upper, broad, flap-like piece, the *labrum; of 
a pair of brown, strongly chitinized, toothed jaws or 
mandibles; of a second pair of jaw-like structures, the 
maxillce, each of which is composed of several parts ; and 
of an under, freely-movable flap, the labium, also com- 
posed of several pieces. Each maxilla bears a slender 
feeler or palpus composed of five segments. The labium 
bears a pair of similar palpi, which are, however, only 
three-segmented. The mandibles and maxillae, which 
are the insect jaws, move laterally, not vertically as with 
most animals. 

Make drawings of the lateral aspect of the head ; of a 
bit of the cornea; of the dissected out mouth-parts. 

Of the three segments of the thoracic region of the 
body, the most anterior one is called the prothorax. It 
is freely movable and has a large hood or saddle-shaped 

* The labrum differs from the other mouth-parts in not being composed of 
a pair of body appendages ; it is simply a fold or flap of the skin of the head. 



i6o ELEMENTARY ZOOLOGY 

piece, the pronotum, on its dorsal aspect, and a blunt- 
pointed tubercle on the ventral aspect. The foremost 
pair of legs is attached to the prothorax. The next 
segment is the mesotJiorax> which is immovaly fused to 
the next thoracic segment. What appendages does it 
bear ? The third segment is the metathorax, which 
besides being fused with the mesothorax in front, is 
similarly fused with the foremost abdominal segment 
behind. What appendages does the metathorax bear ? 

Examine one of the fore legs and note that it is com- 
posed of a series of unequal parts or segments. The 
segment nearest the body is sub-globular and is called 
the coxa; the second segment is smaller than the coxa 
and is called the trochanter ; the third, known as the 
femur, is the largest of all ; the fourth, tibia > is long and 
slender; and the next three, the last of which is the 
terminal one and bears a pair of claws and between them 
a little pad, the pulvillus, are called the tarsal segments. 
Most insects have five tarsal segments. Note the great 
size of the hindmost or leaping legs. Determine the seg- 
ments of the middle and hindmost legs. Make a draw- 
ing of a fore leg. 

Examine the wings. In what ways do the front wings 
differ from -the hind wings ? The front wings are known 
as the wing covers or tegmina. Note how the hind wings 
fold up like a fan, and are covered and protected by the 
wing covers. Draw the wings. 

The abdomen is composed of a number of segments 
most of which resemble each other. The first segment 
(immediately behind the metathorax) has its dorsal and 
ventral parts widely separated by the cavities for the in- 
sertion of the hindmost legs. The ventral part of this 
segment is dovetailed into the ventral part of the meta- 
thorax and appears to be part of it. In the dorsal part 
of this segment there is on each side a spot where the 



BRANCH ARTHROPODA; CLASS INSECT A : THE INSECTS 161 

cuticle is only a thin membrane. At these places are 
the auditory organs or ears of the locust. The thin 
membranes are the tympana. Only the various kinds of 
locusts and those insects closely related to them have ears 
of this kind. Most other insects are believed to have the 
sense of hearing situated in the antennae. 

The abdominal segments from second to eighth are ring- 
like in form and are without appendages. There is on 
the side of each of these segments near its front margin a 
tiny opening or pore called a spiracle. These spiracles 
are the breathing pores of the locust, which does not take 
in air through its mouth or any other opening in the head. 
There is a spiracle near each ear in the first abdominal 
segment, and one on each side of the mesothorax near 
the insertion of the middle legs. 

The terminal segments of the abdomen are provided 
with certain processes which are different in male and 
female. The female has at the tip of its abdomen two 
pairs of strong, curved pointed pieces which compose the 
ovipositor, or egg-laying organ. The opening of the 
oviduct lies between the pieces. The male has a swollen 
rounded abdominal tip, with three short inconspicuous 
pieces on the dorsal surface. 

Make a drawing of the lateral aspect of the abdomen 
of a female locust; also, of a male. 

For a more detailed account of the external anatomy of 
a locust see Comstock and Kellogg's "Elements of In- 
sect Anatomy, " chap. II. 

The external structure of the grasshopper should be 
carefully compared with that of the crayfish; pay special 
attention to the mouth-parts and legs. 

The teacher should point out the homologies and 
modifications. 

Life-history and habits. — The eggs of the locust are 
laid in the autumn in the ground in bare dry places, 



t62 elementary zoology 

as roadsides, closely-grazed pastures, etc. The female 
thrusts her strong ovipositor into the soil, and by opening 
and shutting it, thus boring, pushes in the abdomen for 
about two thirds its length. The eggs, about one hun- 
dred, are then deposited in a capsule or pod. The young 
locusts hatch in the following spring. When just 
hatched they resemble the parent locust in general 
appearance and structure except that they lack wings, 
and are of course very small. The young locusts are 
gregarious, congregating in warm and sunny places. 
They feed on green plants and travel about by walking 
and hopping. At night they try to find shelter under 
rubbish in the fields. They feed voraciously and grow 
rapidly, reaching maturity in about two months. During 
this post-embryonic development and growth they molt 
(shed the chitinous exoskeleton) five times. After the 
first molt indications of the wings appear in the shape of 
small backward and downward prolongations of the pos- 
terior margins of the dorsum of the mesothorax and 
metathorax. With each succeeding molt these wing- 
pads, or developing wings, are larger and more wing-like, 
until after the last molting they appear fully developed. 
With each molting, too, there is a marked increase in 
size of the locust, the average length of the body just 
before the first moult being 4.3 mm., before the second 
6.8 mm., before the third 9 mm., before the fourth 14 
mm., before the fifth 17 mm., and after the fifth (the full- 
grown stage) about 26 mm. 

The molting is an interesting process, and can be 
readily observed. The young locust ready for its last 
molt crawls up some post, weed, grass stalk, or other 
object, and clutches this object securely with the hind 
feet. The head is generally downward. The locust 
remains motionless in this position for several hours, when 
the skin suddenly splits along the back from the middle 



BRANCH ARTHROPODA ; CLASS INSECT A : THE INSECTS 163 

of the head to the base of the abdomen. By steady 
swelling and contracting and slight wriggling, lasting for 
half an hour to three-fourths of an hour, the old skin is 
completely shed, and the wings spread out. In an hour 
the wings are dry and the new chitinized exoskeleton 
firm enough for flying, or crawling about, and in another 
hour the locust begins to eat. 

The red-legged locust does considerable damage to 
cultivated crops, but its injuries are insignificant compared 
with the tremendous losses occasioned by a near relative, 
the Rocky Mountain Locust {Melanophis sprehis). This 
locust has its breeding-grounds on the high plateaus of 
the Rocky Mountain region, but it sometimes migrates in 
countless numbers southeast over the plains and into the 
great grain-fields of the Mississippi valley. Such migra- 
tions occurred in 1866, 1867, 1874 (in this year eighteen 
hundred and forty two families in Kansas were reduced 
to destitution by the utter wiping out of their crops by 
the locusts) and 1876. With the settling-up of the 
regions in which the Rocky Mountain locust breeds, there 
seems to have come a change of conditions, so that no 
great migrations have occurred since 1876. 

THE GREAT WATER-SCAVENGER BEETLE (Hydrophilus sp.) 

Technical Note. — The great water-scavenger beetles are 
large, black, elliptical insects common in quiet pools where they 
may be found swimming through the water, or crawling among the 
plants growing on the bottom. They are an inch and a half long 
and are readily distinguishable from all other water insects except 
the predaceous diving beetles (Dyticus). The antennae of Hydro- 
fihilus, however, are thickened (clavate) at the tip, while those of 
Dyticus are thread-like for their whole length. The beetles may 
be readily collected with a water-net, and kept alive in glass jars 
or aquaria in water containing decaying vegetation. 

External structure (fig. 39). — Is the body of the water- 
beetle composed of segments ? Can you make out three 
body-regions, head, thorax and abdomen ? As in the 
locust the vietatlwrax is fused with the first abdominal 



164 



ELEMENTARY ZOOLOGY 



mouth-parts 
0C \ ^K J- — -^maxillary palp 1 

head 



labium 
compound ey&- 



antenna 



coxa- 
trochanter— 



femur-'' 
tibia-' 



tarsal segmerits 



~prothorax 
jrnesothorax 
metathorax 




^abdomen 



Fig. 39. — Ventral aspect of male great water-scavenger beetle, 

Hydrophilus sp. . 



BRANCH ARTHROPODA ; CLASS INSECT A : THE INSECTS 165 

segment and with the mesothorax, while the prothorax 
is freely movable, and is covered above by a strong shield. 
The chitin armor of the whole body is specially heavy 
and strong, affording a great protection to the insect. 

On the flattened head note the compound eyes and the 
peculiarly-shaped nine -segmented antennae. Are there 
way ocelli? Dissect out the mouth-parts. The beetle's 
mouth is fitted for biting, the mouth-parts being in general 
character like these of the locust, with distinct flap-like 
labrum, dentate mandibles, jaw-like maxilUe with long, 
slender, four-segmented palpi and lip-like labium with 
three-segmented palpi. Make drawings of the antennae 
and mouth-parts. 

Note the character of the thoracic segments. Ex- 
amine the wings and legs. The fore wings are modified 
into strong horny sheaths, or elytra, which completely 
cover and protect the folded hind wings. The hind wings 
are large and membranous. How are they folded ? Note 
the adaptation of the middle and hind legs for swimming. 
Determine the various segments of the legs, i.e. coxa, 
trochanter i femur i tibia and tarsus. Note the long longi- 
tudinal median keel on the ventral aspect of the thorax. 

The abdomen articulates with the metathorax by the 
full width of the broad first abdominal segment. It is 
composed of a series of segments without appendages, of 
about equal length but decreasing in width from in front 
backwards. Of how many segments does the abdomen 
seem to be composed when viewed from the ventral 
aspect ? From the dorsal ? 

Make a drawing of the ventral aspect of the whole 
body. 

Technical Note. — After examining the abdomen thus far, re- 
move it from the rest of the body, and boil it in dilute potassium 
hydrate (KOH) in a test-tube. This will soften and partially bleach 
the body wall, 



166 ELEMENTARY ZOOLOGY 

Examine the softened specimen, and note that at least 
two additional segments are to be found retracted or tele- 
scoped into the apparently last segment. The character 
of these terminal abdominal segments differs in male and 
female individuals, and specimens of both sexes should be 
examined. (The males can be distinguished from the 
females by the peculiar pad-like expansion of the last 
tarsal segment of the fore legs.) Pull out the retracted 
segments, and note that they are unevenly chitinized, 
parts of their surface being simply membranous. Project- 
ing backwards are several long-pointed processes. The 
female has but one retracted segment. Though the 
females of many insects possess more or less elaborately 
developed egg-laying organs, this is not the case with the 
beetles. Look for spiracles near the lateral margins of 
the dorsal surface of the abdomen. How many pairs are 
present ? 

Internal Structure (fig.40).— Technical Note.— If fresh speci- 
mens are to be had, kill by dropping into the cyanide bottle (see p. 
463)- Specimens preserved in a 5$ solution of chloral hydrate may 
be used if necessary. When putting specimens into this solution a 
small slit should be cut through the body wall to allow the preserv- 
ative to enter the body cavity. When ready to dissect a specimen 
cut off the elytra and wings close to the base, and carefully remove 
all of the dorsal wall of the abdomen and thorax and the median 
portion of the dorsal wall of the head. Pin out, ventral side down, 
under water in a dissecting-dish. 

Note in the median dorsal line of the abdomen a pale 
transparent longitudinal vessel, the heart or dorsal vessel. 
Note on each side of it six prominent triangles or " Vs " 
with apex of each directed laterally, the posteror three 
smaller than the anterior three of each side. These tri- 
angles are formed by respiratory tubes or trachea. From 
each spiracle or breathing-pore there extends into the 
body a respiratory tube or trachea. These lateral tracheae 
join a main longitudinal trachea on each side, from which 



BRANCH ARTHROPODS ; CLASS INSECT A : THE INSECTS 167 

are given off branches, which in turn repeatedly subdivide, 
until all parts of the body are ramified by tracheae, large 
and small, bringing air to all the tissues. The oxygen is 



brain 
oesophagus- 



..ganglia 




^alimentary 
canal 
1 ventral nerve 
chain 



Malpighian 
tubules 



oviduct'*' egg-tupes 2 

accessory glandb' tectum 

\receptaculum~ seminalis 
Fig. 40. — Dissection of female great water-scavenger beetle, Hydrophilns 
sp., the heart and tracheae being cut away. 



taken up from this air, and carbonic-acid gas is given up 
to it, when it passes out of the body again through the 
spiracles. Thus in the insects oxygen and carbonic-acid 



1 68 ELEMENTARY ZOOLOGY 

gas are not carried by the blood but by special air-tubes. 
The respiratory system of insects is very different from 
that of other animals. 

Mount a bit of trachea in glycerine on a glass slide and 
examine under the microscope. Note the fine spiral line 
(looking like transverse annular striations) which is a 
thickening of the chitinous inner wall of the tube and 
which by its elasticity keeps the tracheal tubes open. 

The heart, already noted, is composed of a longitudinal 
series of very thin-walled chambers, each with a pair of 
lateral openings into the body-cavity and with terminal 
openings into the adjacent chambers. The blood, which 
is colorless or greenish or yellowish, is sent forward 
through the successive heart chambers by regular contrac- 
tions until it finally pours from the most anterior chamber 
freely into the body-cavity. Here it bathes the body- 
tissues, flowing perhaps in regular paths, giving up food 
to the tissues and taking up food from the alimentary 
canal, until it finds its way through the lateral openings 
into the heart chamber again. There are no arteries or 
veins. 

Note the large mass of muscles in the meta thorax. 
Note, by attempting to remove it, that the anterior part 
of the muscle mass is attached to a chitinous partition-wall 
between the meso- and meta-thorax. Remove this parti- 
tion-wall (and one between the metathorax and abdomen) 
and note that certain muscles run deeply down into the 
body. By pulling on the bits of chitin to which the 
muscles are attached, the muscles (if they have not been 
cut) can be stretched to the length of three-quarters of an 
inch. When released they will contract. (This stretch- 
ing and contracting takes place only in fresh specimens.) 
What are these large and numerous muscles of the thorax 
for? 

Remove the thin membrane stretching over the abdomen 



BRANCH ARTHROPODS ; CLASS IN SECT A: THE INSECTS 169 

and in which the heart and tracheal " Vs " lie, and note 
immediately underneath it the large coiled intestine with 
a knot of greenish yellow threads in the centre. Carefully 
uncoil and pin out the intestine, cutting away the tying 
tracheae, but being careful not to cut other structures. 
Work out the full length of the alimentary canal, noting 
the oesophagus, the widened crop behind it, and the long 
intestine. From the intestine arise several greenish 
yellow threads, the Malpighian tubules. These are the 
excretory organs of the insect. What is the total length 
of the alimentary canal ? 

The reproductive organs, consisting of a pair of glands 
(egg-glands or sperm-glands) with a pair of tubes which 
unite before reaching the body-wall and have a common 
external opening, may now be seen. These should be 
removed, thus exposing the ventral nerve-chain in the 
abdomen. To expose the chain in the thorax it will be 
necessary to pick away carefully the muscles. As in the 
crayfish, the central nervous system in the beetle consists 
of a ventral nerve-chain, a brain or supra-oesophageal 
ganglion and a pair of circum-oesophageal commissures 
connecting the brain and the foremost ganglion (infra- 
esophageal) in the ventral chain. There are, in the 
ventral chain, four ganglia in the thorax and four in the 
abdomen. The large nerves running from the brain to 
the compound eyes and to the antennae can be traced. 

Make a drawing showing the nervous system. 

Life-history and habits.— The eggs, usually about 
one hundred, are deposited in a silken sac or case which 
is spun by the female, and either floats freely or is attached 
to the under sides of the leaves of aquatic plants. This 
egg-case is not wholly filled with eggs but has a consider- 
able air-chamber in it, causing it to float. It is oval in 
shape, and has a peculiar curved horn-like projection at 
the upper end. In sixteen or eighteen days the young 



170 ELEMENTARY ZOOLOGY 

water-scavenger beetles hatch as elongate, wingless, 
active larvae, provided with three pairs of legs and strong 
jaws. They remain for a short time after hatching in the 
egg-case, feeding on each other ! After they issue from 
the case they feed on flies or other insects which fall into 
the water, and on snails. They breathe through a pair 
of spiracles situated at the posterior tip of the abdomen, 
coming to the surface and thrusting this tip up so that the 
spiracles are out of water. They grow rapidly, molting 
three times before becoming full grown. They attain a 
length of nearly three inches. When full grown they 
leave the water, crawling out on the damp shore of the 
pond or stream, and burrow into the soil for a few inches. 
Here they molt again, or pupate as it is called, changing 
to a non-feeding, quiescent stage called the pupal stage. 
The pupa is the stage in which the great changes from 
wingless, crawling and swimming, short-legged, long, 
slender-bodied larva to winged, swimming and flying, 
long-legged, compact, broad-bodied adult are completed. 
Late in the summer or in the fall the pupal skin breaks 
and the adult issues. It works its way to the surface of 
the ground, and betakes itself to the nearest water. 

The water-scavenger beetle shows in its post-embryonal 
development a " complete metamorphosis " as contrasted 
with the "incomplete metamorphosis' of the locust. 
Wherever among insects similar changes occur, the young 
issuing from eggs as larvae only remotely resembling the 
parent, and these active feeding larvae changing finally 
into more or less quiescent, strictly non-feeding pupae, 
which finally change into the active adults, a complete 
metamorphosis is said to exist. All the beetles, the 
butterflies and moths, the two-winged flies, the ants, bees 
and wasps, and certain other groups of insects undergo in 
their post-embryonic development a complete metamor- 
phosis. The crickets, katydids, the sucking bugs, the 



BRANCH ARTHROPODA; CLASS INSECT A : THE INSECTS 17 x 

May-flies, the white ants and numerous other insects 
have, like the locust, an incomplete metamorphosis, that 
is, the young when hatched resemble in most respects, 
except in the absence of wings, their parents. 

The adult water-scavenger beetle feeds chiefly on 
decaying vegetation in the water, but instances of the 
taking of other insects and of snails have been noted. 
Although an aquatic insect the beetle, like its larva, has 
no gills for breathing the air which is mixed with the 
water, but has to come to the surface occasionally to 
obtain air. This it does in an interesting way, which 
should be carefully observed by the pupils. The air is 
received and held by a covering of fine hairs on the ven- 
tral surface of the body, so that a considerable supply may 
be carried about by the beetle while underneath the sur- 
face. The beetles often leave the water by night, flying 
abroad to other ponds or streams. In winter the beetles 
hibernate, burying themselves in the banks of the ponds 
which they inhabit. 

For a good account, with illustrations, of the water- 
scavenger beetle's life-history see Miall's " Natural His- 
tory of Aquatic Insects," pp. 61-87. 

THE MONARCH BUTTERFLY (Anosia plexippus) 

Technical Note. — The Monarch or Milkweed butterfly is dis- 
tributed all over the country. It is large, and red-brown in color, 
and lays its eggs on milk weeds where the greenish yellow and black- 
banded larvae (caterpillars) may be found feeding. The covering 
of scales conceals the outlines of the various external parts, but 
these scales may be easily removed with dissecting needle and a 
small brush. In brushing the scales from the head care must be 
taken not to break of the mouth-parts. 

External structure (fig. 41). — Note the three body- 
regions, head, thorax and abdomen. Is the body seg- 
mented ? Note the dark color and firm character of the 
chitinized cuticle. 



172 



ELEMENTARY ZOOLOGY 



Note on the head the large compound eyes. Note the 
tumid convex clypeus which composes most of the anterior 
aspect of the head. Are ocelli present ? Compare the 
antenna? with those of the locust and water-beetle. Com- 
pare also the month-parts and note that they differ radi- 
cally from those of the locust and beetle. They are not 
fitted for biting, but for sucking up liquid food (the nectar 
of flowers). Note the absence of a movable flap-like 
labrum (a minute narrow stiff piece, bearing at each lateral 




compound eye, 
antennae 



prothorax 



labial 
palpi 

proboscis 



tarsal segments 

Fig. 41. — Body of the monarch butterfly, Anosia plexippus, with scales re- 
moved to show the external parts. 

end a small group of fine brown hairs, represents the 
labrum), the entire absence of mandibles, and the absence 
of a movable flap-like labium. The labium is a fixed 
chitinized triangular piece forming part of the floor of the 
head. Note the long slender proboscis coiled up like a 
watch-spring. (In fresh specimens this proboscis can be 
uncoiled and will be found flexible. If dried or alcoholic 
specimens are being studied, the head of the butterfly 



BRANCH ARTHROPODA ; CLASS INSECT A : THE INSECTS 173 

should be removed and softened in warm water before the 
mouth-parts are examined.) On either side of this 
proboscis is a peculiar pointed process which rises from 
the under side of the head. These processes are the 
labial palpi and serve to protect the sucking proboscis. 
The proboscis itself is composed of the two greatly modi- 
fied maxilla?. Instead of being short, jaw-like and com- 
posed of several pieces as in the locust, in the butterfly 
each maxilla is a slender, flexible half tube applied against 
its mate on the opposite side in such a way as to form a 
perfect tube long enough to reach into the nectaries of 
flowers when in use and capable of being compactly coiled 
up at other times. Cut across the proboscis and note the 
canal in the centre. Try to separate the two maxillae 
which compose it. 

Make a drawing of the frontal aspect of the head with 
the eyes and appendages. 

Compare the thorax with that of the beetle and that of 
the locust. The prothorax is a freely movable narrow 
ring or collar. The rnesothorax and metathorax are fused 
to form a large convex mass, of which fully five-sixths is 
rnesothorax and only one-sixth metathorax. Try to dis- 
tinguish the boundaries of the two segments. Note the 
three pairs of legs; the differences in size among them, 
and the differences between them and the legs of the 
locust and water-beetle. In one of the legs determine 
the coxa, trochanter \ femur, tibia and tarsal segments. 
Note the differences between the wings of the butterfly 
and those of the locust and beetle. Note that the wings 
are membranous, but are covered with many fine scales 
(fig. 42), as is, indeed, the whole body. Rub off some of 
these scales on a glass slide and examine ; note shape, 
little stem or pedicel of insertion, and longitudinal stria- 
tions. Examine under microscope a bit of wing from which 
some of the scales have been rubbed. How are the scales 



174 



ELEMENTARY ZOOLOGY 



attached to the wing membranes ? How are the scales 
arranged ? Note that the wing is colorless where the 
scales have been removed. All the colors and patterns 
of the wings of butterflies are produced by the scales. 

Make drawings of scales; of parts of denuded wings, 
and of bit of wing covered with scales. 

Remove all or nearly all the scales from a wing and 
note the arrangement of the veins (venation). Compare 
with venation in wings of locust. 

Make drawing showing venation in the butterfly's 
wings. 

The venation of insects' wings is much used in insect 

classification, and the 
various veins have been 
given names. The 
names of the veins in 
the butterfly's wings are 
given in fig. 43. When 
the veins in the w r ings 
of all the various groups 
of insects are studied, it 
is evident that the prin- 
cipal ones are the same 
in all insects, so that 
the costa, sub-custa, ra- 

JbiG. 42. — Bit of wing of monarch butterfly, ' 

Anosia plexippus, magnified to show the dius, media, cubitus and 




scales; some scales removed to show the 
insertion-pits and their regular arrange- 



anal veins of the butter- 



ment. (From specimen.) fly's wings can be com- 

pared with the corresponding veins in the wings of a 
beetle or v/asp or fly. Noting the differences in the num- 
ber and character of branching of these principal veins, 
and the number and disposition of the cross-veins which 
connect the longitudinal veins, the various kinds of insects 
can be to a large extent properly grouped or classified. 
A detailed account of the wing-veins of insects is given 



BRANCH ARTHROPODA ; CLASS INSECT A : THE INSECTS 175 



in Comstock and Kellogg's ki Elements of Insect Anat- 
omy, " chap. VII. 

Of how many segments is the abdomen composed ? 
The first or basal segment is depressed, while the others are 
more or less compressed. The spiracles are, as in the locust, 
situated on the lateral aspects of the abdominal segments. 
What segments bear spir- 
acles ? The terminal seg- 
ments of the abdomen 
differ in the two species. 
In the female the dorsal 
part of the apparently) 
last segment is longer 
than the ventral part and 
is bent down over it form- 
ing a sort of hood over a 
space enclosed partly by 
this hood, partl\- by a 
bluntly -pointed projection 
from the ventral surface, 
and party by the lateral 
margins of the segment. 
In this chamber lies the 

from which the Fig. 43.— Wings of monarch butterfly, 
Tn the male Anosiaplexippus, to show venation ; c, 

costal vein; sc, sub-costal vein; r, radial 
there are several back- vein; cu s cubital vein; a, anal veins. 
1 • _.!_•_ 1 In addition most insects have a vein 

ward - projecting, horny, , ying between the sub costal and ra . 

thin processes. dial veins called the median vein. 

Make a drawing of the lateral aspect of the whole body. 

Life-history and habits. — The tiny, conical, yellowish- 
green eggs of the monarch butterfly are deposited on the 
under side of the leaves of milkweeds (Asdepias) and 
when examined under the microscope are seen to be very 
beautiful little objects finely ribbed with longitudinal and 




opening 
e^o's issue 



transverse striae 



The 



e^srs ar 



laid in April and May 
(depending on the latitude and season) by females which 



176 ELEMENTARY ZOOLOGY 

have hibernated in the adult condition. From the eggs 
the minute, cylindrical, pale-green, black-headed larvae 
hatch in four or five days. As soon as hatched the 
larva devours the eggshell from which it has escaped and 
then feeds voraciously on the milkweed leaves. It grows 
rapidly, and in three or four days a blackish band or ring 
appears on each segment, and for the rest of its life it is 
very conspicuously colored with its black rings on a 
yellowish-green background. It molts three times, and 
in from twelve to twenty days is ready to pupate, or 
change to a chrysalis. 

When ready to pupate the larva usually leaves the 
milkweed plant, and seeks some such protected place as 
the under side of a fence-rail or jutting rock. Here it 
attaches its posterior extremity by a small silken web to 
the rail or rock, and casting its larval skin appears as a 
beautiful pale-green chrysalis with ivory black and golden 
spots. It hangs motionless, and of course without taking 
food, for from a week to two weeks (according to 
season and temperature), when the pupal cuticle breaks 
and the great red-brown butterfly (fig. 165) issues. 

The butterfly feeds (as is indicated by the structure of 
its mouth-parts) very differently from the larva; it sucks 
up by means of its long tubular proboscis the nectar of 
flowers, nor does it confine itself at all to the flowers of 
milkweeds. It is a fine flyer and a great traveller. Many 
thousands of these butterflies often make long flights or 
migrations together. At other times tens of thousands 
of these butterflies congregate in a certain limited area, 
clinging sometimes to the branches of a few trees in such 
numbers and so closely together as to give the tree a 
brown color. Such a " sembling " of monarch butterflies 
occurs every year near the Point Pinos lighthouse on 
the Bay of Monterey, California. The object of this 
assembling together is not understood. Both the larvae 
and adults of the monarch butterfly are distasteful to birds, 



BRANCH ARTHROPODA ; CLASS INSECT A : THE INSECTS 177 

by their possession of an acrid body-fluid. The species 
is thus protected against the most dangerous enemies of 
butterflies, a fact which chiefly accounts for the great 
abundance and wide distribution of the monarch (see 
p. 137). For a full account of the life-history of the 
monarch butterfly, see " Scudder's Life of a Butterfly." 

LARVA OF MONARCH BUTTERFLY {Anosia plexippus) 

Technical Note. — For directions for finding and identifying the 
larvae of the monarch butterfly see p. 171. If larvae (caterpillars) of 
Anosia cannot be found, those of any other butterfly or moth will 
do. Use naked, smooth kinds like cutworms, cabbage worms and 
the like, rather than hairy or spiny ones. Use large specimens. 
Kill the caterpillar with ether or in a cyanide bottle. 

Structure (fig. 44). — As we have learned from the study 
of the life-history of the locust, water-beetle and butterfly, 
some insects are hatched from the egg in a condition 
resembling that of the parents in most structural charac- 
ters. This is true of the locust. Other insects, as the 
beetle and butterfly, are hatched in a form and condition 
apparently very different from that of the parents. The 
external appearance of a beetle or butterfly larva differs 
much from that of the adult or imago of the same indi- 
vidual. It will be of interest to examine more particu- 
larly the structural condition of one of these larvae and to 
compare it with the structure of the adult. 

Is the body segmented ? Is the body composed of 
head, thorax and abdomen f Note the soft, flexible, 
weakly-chitinized condition of the body-wall. How many 
pairs of legs are there ? Where are they situated ? Is 
there any difference in the various legs ? If so, what is 
the difference ? Which of the legs of the larva correspond 
with the legs of the butterfly ? Why ? The prothoracic 
segment and the abdominal segments 1 to 8 each bear a 
pair of spiracles (small blackish spots on the sides). Are 
both compound and simple eyes present ? How many eyes 



i 7 8 



ELEMENTARY ZOOLOGY 




3 



c 



BRANCH ARTHROPODA ; CLASS INSECT A : THE INSECTS 179 

are there ? Are there antcnnce ? Dissect out the month- 
parts. How do they differ from those of the butterfly ? 
Are they more like the mouth-parts of the butterfly or 
more like those of the locust ? 

With fine sharp-pointed scissors make a shallow longi- 
tudinal incision along the whole length of the dorsal wall. 
In a freshly-killed specimen a drop of pale greenish blood 
will issue as the scissors' point is first thrust through the 
skin. Put a droplet of this blood on a glass slide, cover 
with cover glass and examine with high power of the 
microscope. Note that the blood is a fluid containing 
numerous sub-circular or elliptical bodies, the blood- 
corpuscles. Note at least two kinds of corpuscles: most 
abundant a granular, circular kind, the true blood-corpus- 
cles; and rarer, a larger, clear, usually elliptical or oval, 
but sometimes irregular and amoebiform kind, generally 
spoken of as fat-cells. 

Make a drawing of the corpuscles in the field of the 
microscope. 

After making the dorsal longitudinal incision pin out 
the caterpillar in the dissecting-dish with dorsal aspect 
uppermost. When the edges of the skin are pinned back, 
the organs most conspicuous in the body-cavity will be 
the flocculent masses of adipose tissue, the large, simple, 
tubular alimentary canal usually dark or greenish because 
of the color of its contents, and the numerous silvery 
tracheal tubes. In those caterpillars which spin a silken 
cocoon, the silk or spinning-glands are usually long and 
prominent. They lie on either side of the anterior part 
of the alimentary canal, and open by a common duct on 
the labium. Rising from behind the middle of the ali- 
mentary canal maybe found the long, whitish, folded and 
twisted Malpighian tubules. By picking away the fat 
masses, expose the full length of the alimentary canal. 
Note its great size (large diameter). Is it divided into 



i8o ELEMENTARY ZOOLOGY 

distinct regions such as crop, proventriculus, stomach, 
intestine, etc. ? How is it held in place ? Trace the 
principal longitudinal tracheal trunks. Find, if you can, 
a pair of small compact bodies usually somewhat elongate, 
one lying on each side of the posterior part of the alimen- 
tary canal. These are the rudimentary reproductive 
organs. 

Remove the alimentary canal by cutting it off at its 
posterior tip and also in the prothoracic segment. Work 
out now the ventral nerve-cord and ganglia, and the 
supra-cesophageal (brain) and infra-cesopliageal ganglia 
and the commissures in the head. 

In the body of the caterpillar we have found the same 
general disposition of organs as in the body of an adult 
insect, but several differences are nevertheless noticeable, 
viz., the presence of a large quantity of fatty tissue, the 
great size and simple character of the alimentary canal, 
and the undeveloped condition of the reproductive organs. 



OTHER INSECTS 

The class Insecta includes those Arthropods which 
have one pair of antennae (sense appendages), three pairs 
of mouth-parts (oral appendages), and three pairs of legs 
(locomotory appendages). The insects, in further con- 
tradistinction to the crustaceans, are mostly land animals 
and breathe by means of tracheae or tracheal gills. They 
are the most familiar of land invertebrates, and, as already 
mentioned, include more species than are comprised in all 
the other groups of animals taken together. Beetles, 
moths and butterflies, flies, wasps and bees, dragonflies 
and grasshoppers are familiar members of the class of 
insects, but spiders, mites, scorpions, centipeds and 
thousand-legged worms are not true insects and should 



BRANCH ARTHROPOD A ; CLASS INSECT A : THE INSECTS 181 



not be so miscalled. These last belong to the branch 
Arthropoda but to other classes than the class Insecta. 
While insects are found living under most diverse condi- 
tions on land, that is, on the ground, in the leaves, fruits 
and stems of plants, in the trunks of trees or in dead 
wood, in the soil, in decaying animal or plant matter, as 
parasites on or in other animals, and in all fresh- water 
ponds and streams, they do not live in ocean water. A 
few species live habitually on the surface of the ocean, and 
a few other forms are found habitually on the water- 
drenched rocks and seaweeds between tide lines. The 
varied habits of insects, their economic relations with 
man. the beauty and grace of many of them, and the 
readiness with which they may be collected, reared and 
studied, renders them unusually fit animals for the special 
attention of beginning students of zoology. 

Body form and structure. — The segments composing 
the body of an insect 
are grouped to form 
three body-regions, the 
head, thorax, and abdo- 
men. The head of an 
adult insect appears to 
be a single segment or 
body-ring, but in reality 
it is composed of several 
segments, probably 
seven, completely fused. 
The head bears the eyes, 
antennae and the mouth- 
parts. The thorax is 
made up of three seg- 
ments, each segment 
bearing a pair of legs. 
From the dorsal side of the hinder two thoracic segments 




Fig. 45. — A wingless insect; the American 
spring-tail, Lepidocyrtas americanus, 
common in dwelling-houses. The short 
line at the right indicates the natural 
size. (From Marlatt.) 



182 ELEMENTARY ZOOLOGY 

arise the two pairs of wings which are the most striking 
structural features of insects. Not all insects are winged, 
(fig. 45), and of those which are a few have only one pair 
of wings, but the great majority of them have two pairs of 
w T ell-developed wings (fig. 46), which give them, as com- 
pared with the other animals we have studied, a new and 
most effective means of locomotion. The great numbers 




Fig. 46. — A four- winged insect; a stone fly, Per la sp., common about 
brooks. (From Jenkins and Kellogg.) 

of insects and their preponderance among living animals 
is undoubtedly largely due to the advantage derived from 
their power of flight. The hindmost part of the body, 
the abdomen, is composed of from seven to eleven seg- 
ments, only the last one or two of which are ever provided 
with appendages. When such posterior abdominal 
appendages are present they form egg-laying or stinging 
or clasping organs. 



BRANCH ARTHROPODA; CLASS INSECT A : THE INSECTS 183 

The body-wall is usually firm and rigid, with thinner 
flexible places between the segments and body-parts for 
the sake of motion. The body-wall is composed of a 
cellular skin or hypoderm, and an outer non-cellular 
cuticle in which is deposited a horny substance called 
chitin. This chitinous cuticle or exoskeleton serves as 
an armor or protective covering for the soft body within, 
and also as a point of attachment for the many muscles 
of the body. 

Insects vary a great deal in regard to shape and ap- 
pearance of the body, and certain of the external organs 
are greatly modified in different insects to adapt them to 
the varied conditions under which they live. Especially 
interesting and important are the variations in the char- 
acter of the mouth-parts and wings, the organs of food- 
getting and locomotion. In our consideration later of 
some of the more important groups of insects the modifica- 
tion of these parts will be specially referred to. Despite 
the great number of insects, however, and their varied 
habits of life, a strong uniformity of body-structure is 
noticeable, all of them holding pretty closely to the 
typical body-plan. 

The most interesting feature of the internal anatomy of 
the insect body is the respiratory system. Insects breathe 
through tiny paired openings, called spiracles, in the sides 
of the abdominal (and sometimes the thoracic) segments 
(the number and disposition of the pairs of spiracles varying 
much in different insects). These spiracles are the external 
openings of an elaborate system of air-tubes or tracheae 
(fig. 47) which ramify throughout the whole body and carry 
air to all the organs and tissues. The blood has apparently 
nothing to do with respiration as it has in the vertebrate 
animals, where it carries oxygen to all the body tissues. 

The other systems of organs are well developed and in 
many respects more complex and elaborate than those of 



1 84 



ELEMENTARY ZOOLOGY 



any of the other invertebrates. The muscular system 
comprises a large number of distinct mus- 
cles, usually small and short, which are 
disposed so as to make very effective the 
various complex motions of antennae, 
mouth-parts, legs, wings, and egg-laying 
organs. The muscles appear to be 
very delicate, being almost colorless 
when fresh, but they have a high 
contractile power. The alimen- 
tary canal is di- 
vided into various 
special re- 
gions, a s 
rynx, cesopha- 
Fig, 47.— Piece of gus, crop, fore 

trachea (air- tube) , . ., 

from the larva of stomach or gizzard, 

the giant-crane- digesting stomach, 
fly. (Photo-micro- 




\ 




graph by Geo. O. an d small and large in- 

Mitchell.) testine. From the canal 

just at the point of union of the digesting 
stomach (ventriculus) and the small in- 
testine rise the so-called Malpighian 
tubules, which are excretory organs. 
They are long slender diverticula of the 
alimentary canal, and are typically six 
(three pairs) in number. The circula- 
tory system is composed of a tubular 
vessel running longitudinally through the 
body in the median line just under the 
dorsal wall. It is composed of a series 
of chambers or segmental parts, which 
by a rhythmic contraction and expansion 
propel the blood anteriorly and into a 
short, narrow, unsegmented anterior portion of the vessel 



Fig. 48. — The anten- 
na of a carrion bee- 
tle, with the termi- 
nal three segments 
enlarged and flat- 
tened, and bearing 
many li smelling- 
pits,'' the antenna 
thus serving as an 
olfactory organ. 
(Photo - micrograph 
by Geo. O.Mitchell.) 



BRANCH ARTHROPODA ; CLASS INSECT A : THE INSECTS 185 

which may be called the aorta. There are no other 
arteries or veins, the blood simply pouring out of the 
anterior end of the dorsal vessel into the body-cavity. It 
bathes the body tissues, flowing usually in regular channels 
without walls. It re-enters the dorsal vessel through 
paired lateral openings in the chambers. 

The main or central nervous system consists of a large 
ganglion, the "brain," situated in the head above the 




Fig. 49. — A section through the compound eye (in late pupal stage) of the 
blow-fly, Calliphora romitoria. In the centre is the brain, with optic 
lobe, and on the right-hand margin are the many ommatidia in longi- 
tudinal section. (Photo-micrograph by Geo. O. Mitchell.) 

oesophagus, which sends nerves to the antennae and eyes, 
a ganglion in the head below the oesophagus connected 
with the brain by a short commissure on each side of 
the oesophagus, and sending nerves to the mouth-parts; 
and a ventral nerve-chain composed of a pair of longitudinal 



1 86 ELEMENTARY ZOOLOGY 

commissures lying close together and running from the 
head to the next to the last abdominal segment, which 
bears a series of segmentally disposed ganglia, each 
ganglion being composed of two ganglia more or less 
nearly completely fused. There is, in addition, a lesser 
system called the sympathetic system, which comprises a 
few small ganglia and certain nerves which run from 
them to the viscera. The function of the nervous system 
of insects reaches a very high development among the 
so-called ' ' intelligent insects ' and certain extraordi- 
narily complex and interesting instincts are possessed by 
many forms. The social or communal habits of the ants, 
bees, and wasps and the habits connected with the deposi- 
tion of the eggs and the care of the young exhibited by 
the digger wasps and other insects are of extreme 
specialization. The organs of special sense are highly 
specialized, the sense of smell (fig. 48) reaching in par- 
ticular a high degree of perfec- 
tion. One of the compound eyes 
(figs. 49 and 50) may contain as 
many as 30,000 distinct eye- 
elements or ommatidia, but the 
sight is probably in no insect 
very sharp or clear. Among 
insects there are organs of hear- 
ing of two principal kinds. In 

Fig. 5o.-Part^omea, snow- one kind the organ for taking up 
ing facets, of the compound t j ie sound-waves is a group of 

eye of a horse-fly ( Therioplec- . . 

tes sp.). (Photo-micrograph vibratile hairs usually situated on 

by Geo. O. Mitchell.) the antenn2e) as i s t he Case with 

the mosquito; in the other kind, it is a stretched mem- 
brane or tympanum such as is found in the fore leg of a 
cricket or katydid or on the first abdominal segment of 
the locust (fig. 51) 

The sexes are distinct in insects, and there is often a 




BRANCH ARTHROPOD A ; CLASS INSECT A : THE INSECTS 187 

marked sex dimorphism; in numerous species the males 
are winged while the females are wingless, and in a few 
cases this condition is reversed. Where there is a 
difference in size between male and female, the females 




Fig. 51. — The auditory organ of a locust (Melanoplus sp.). The large clear 
part in centre of the figure is the thin tympanum, with the auditory 
vesicle (small black pear-shaped spot) and auditory ganglion (at left of 
vesicle and connected with it by a nerve) on its inner surface. (Photo- 
micrograph by Geo. O. Mitchell.) 



are usually the larger. Fertilization of the egg takes 
place in the body of the female and, strangely, this fertil- 
ization is effected after the eggshell has been formed. In 
all insect eggs there is a minute opening in one pole of 
the eggshell called the micropyle through which the 
sperm-cells enter. In a few cases the young are born 
alive, but such a viviparous condition is exceptional. In 



i88 



ELEMENTARY ZOOLOGY 



a few species, too, young are produced parthenogeneti- 
cally, that is, are produced from unfertilized eggs. And 
in the case of a few insect species male individuals are 
not known. 

Development and life-history. — The young insect 
when just hatched from the egg either resembles, except 
for the absence of wings, its parent in general appearance 
as in the case of the locust, or it may, as in the butterfly, 
emerge in a form very unlike the parent. In the first 
case the young has simply to grow, that is, to increase 





Fig. 52. — The young (at left) and adult (at right) of the bed-bug, Acanthia 
lectnlaria, a wingless insect with incomplete metamorphosis. (After 
Riley.) 



in size, to develop wings, and to make some other not 
very obvious developmental changes in order to become 
fully grown. But in the case of the butterfly, and 
similarly in the case of all other insects as the flies, 
beetles, bees et al., whose young hatch in a larval condi- 
tion differing markedly from the adult, some radical and 
striking developmental changes occur before maturity is 
reached. Such insects are said to undergo complete 
metamorphosis in their development, while those insects 
like the locusts, the sucking-bugs, white ants, and others, 



BRANCH ARTHROPODA ; CLASS INSECT A : THE INSECTS 189 

the just hatched young of which resemble their parents, 
are said to have an incomplete metamorphosis (fig. 52). 

In the case of insects with complete metamorphosis, 
the young hatches as an active grub or worm-like feeding 
larva which increases in size, casting its skin or molting 
several times in its growth. Finally after the last larval 
molt (fig. 53) called pupation the insect appears in a 




Fig. 53. — The larva of the violet tip butterfly, Polygonia interragationis. 
making its last molt, i.e. pupating. (Photograph from life.) 

quiescent non-feeding stage called the pupa (fig. 54), and 
encased in an extra thick and firm chitinous exoskeleton. 
The immovable pupa is sometimes concealed underground, 
sometimes enclosed in a silken cocoon spun by the larva 
just before pupation, or is in some other way specially 
protected. It is in this pupal condition that the great 
changes from wingless, often legless, worm-like larva to 



190 



ELEMENTARY ZOOLOGY 



winged, six-legged, graceful imago of adult stage are 
completed, and with the molting of the chitinous pupal 
cuticle the metamorphosis or development of the insect 
is completed. As a matter of fact many of the special 
organs of the adult, the legs and wings, for example, 
begin to develop as little buds or groups of cells in the 
body of the larva, and when the larva is ready to pupate 




Fig. 54. — Chrysalid (pupa) of the violet tip butterfly, Polygonia inte'rraga- 
tionis. From this chrysalid issues the full fledged butterfly. (Photo- 
graph from life.) 

these imaginal wings and legs are drawn out to the 
external surface of the body, and may be readily recog- 
nized as they lie on the ventral surface of the pupa folded 
and closely pressed to the body surface. In recent years 
the study of the post-embryonic development of insects 
with complete metamorphosis has revealed some re- 
markable changes of the internal organs which result in 
a nearly complete disintegration or breaking down of 



BRANCH ARTHROPODA ; CLASS INSECT A : THE INSECTS 291 

most of the internal organs of the larva (fig. 55) and a 
rebuilding of the organs of the adult from primitive be- 
ginnings. 

The habits of the larvae of insects with complete meta- 
morphosis and of the young of some insects with incom- 
plete metamorphosis often differ markedly from the 




Fig. 55. — A cross-section of the body of the pupa of a honey-bee. showing 
the body cavity filled with disintegrated tissues, and (at the bottom) a 
budding pair of legs of the adult, the larva being wholly legless. 
(Photo-micrograph by Geo. O. Mitchell.) 

habits of the adults, and as the habits and instincts of 
insects are remarkably specialized, the study of their be- 
havior and of the structural and physiological modifica- 
tion which their varied habits of life have brought about 
is of much interest and significance. In later paragraphs 
this phase of insect study will be again referred to. 

Classification. — Much attention has been paid to the 
classification of insects and the 300,000 (approximately) 
known species have been variously grouped together into 
orders by different entomologists. A subdivision of the 
class Insecta into five orders was proposed by Linnaeus 
about 1750 and was used until comparatively recently. 
Since then, however, numerous other arrangements have 
been proposed, all of them agreeing in increasing the 



I9 2 ELEMENTARY ZOOLOGY 

number of orders by breaking up some of the old ones 
into two or more new ones. The classification adopted 
in the text-book * of zoology which we have made our 
reference in classification is an 8-order system. The 
latest English t text-book in entomology adopts a 
9-order system, while the principal American \ text-book 
on this subject divides the insects into nineteen orders. 

The classification depends chiefly on the character of 
the post-embryonic development, that is, on whether the 
metamorphosis is complete or incomplete, and on the 
structural character of the mouth-parts and wings. In 
the following paragraphs a few of the larger insect orders, 
with some special representatives of each, will be briefly 
considered. 

The best American text-book of the classification and 
habits of insects is Comstocks' "Manual of Insects.' 
For an account of the structure of the wings and mouth- 
parts of various insects see Comstock and Kellogg's 
"Elements of Insect Anatomy." 

Orthoptera : the locusts, cockroaches, crickets, katy- 
dids, etc, — Technical Note. — Obtain specimens of crickets or 
katydids, and cockroaches, and compare the external body struc- 
ture with that of the grasshopper; examine especially the wings, 
mouth-parts, legs, and egg-laying organs. Note that the hindmost 
legs of the cockroach are not fitted for leaping but for running. Note 
the sound-making (stridulating) organs on the bases of the fore wings 
of the male katydids and crickets. Note the auditory organs (tym- 
pana) in the fore tibise of the katydids and crickets. Crickets can 
be easily kept alive in breeding-cages in the laboratory and their 
feeding habits and much of their life-history observed. The growth 
of the young and the development of the wings can be noted, and 
will be found to be essentially similar to the conditions already 
found in the case of the locust. 

The locust studied as one of the examples of the class 
Insecta belongs to the order Orthoptera, which also in- 

* A Text-book of Zoology, Parker & Haswell, 1897. 

f The Cambridge Natural History, vol. V, 1895. vol. VI. 1899. 

\ A Manual for the Study of Insects, J. H. and A. B. Comstock, 1897. 



BRANCH ARTHROPODA; CLASS INSECTA : THE INSECTS 19, 




Fig. 56. — The house cricket, 
male (a) and female (b). (From 
Marktt.) 



eludes the cockroaches, crickets (fig. 56), katydids and 
green grasshoppers, the walking-stick or twig insects, the 
praying mantis and others. 
The members of this order all 
have an incomplete metamor- 
phosis, and in all the mouth- 
parts are fitted for biting and 
the fore wings are more or 
less thickened and modified to 
serve as covers or protecting 
organs for the broad, plaited, 
membranous hind wings, which 
are the true flight organs. The 
hind legs of locusts, grasshop- 
pers, crickets, and katydids are 
very large, and enable the in- 
sects to leap; the legs of the cockroaches are fitted for 
swift running; the fore legs of the praying mantis are 
fitted for grasping other insects which serve as their food, 
and the legs of the walking-stick (fig. 162) are long and 
slender and fitted for slow walking. The shrill singing of 
the crickets and katydids and the loud "clacking" of 
the locusts are all made by stridulation, that is, by 
rubbing two roughened parts of the body together. The 
sounds of insects are not made by vocal cords in the 
throat. The male crickets and katydids (for only the 
males sing) have the veins of the fore wings modified so 
that when the bases of the wings are rubbed together 
(and when the cricket or katydid is at rest the base of 
one fore wing overlaps the base of the other) a part of 
one wing called the " scraper " rubs against a part of the 
other called the "file' and the shrilling is produced. 
The sounds of locusts are produced by the rubbing of 
the inside of the hind leg against the outside of the fore 
wing when the insect is at rest, or by striking the front 



194 



ELEMENTARY ZOOLOGY 



margin of each hind wing against the hind margin of each 
fore wing when the locust is flying. For hearing the 
Orthoptera are provided with auditory organs having the 
character of tympana or vibrating membranes. In the 
locusts these ears (fig. 51) are situated on the dorsal 
surface of the first abdominal segment; in the katydids 

and crickets they are in the tibiae 
of the fore legs. The food of 
locusts, crickets, and katydids is 
vegetable, being usually green 
leaves; the cockroaches eat either 
plant or animal substances fresh 
or dry, while the praying mantis 
is predaceous, feeding on other 
insects which it catches in its 
strong grasping fore legs. The 
walking-stick or twig insect is an 
excellent example of what is called 
' ' protective resemblance ' ' among 
animals. Indeed most of the 
Orthoptera are so colored and 
patterned as to be almost indistin- 
guishable when on their usual rest- 
ing- or feeding-grounds. Some 
of the tropical Orthoptera carry 
to a marvelous degree this modi- 
fication for the sake of protection. 
(In this connection read Chapter 
XXXI referring to li Protective Resemblances ".) 

Odonata and Ephemerida : the dragon- flies and May- 
flies. — Technical Note. — Obtain specimens of adult and imma- 
ture dragon-flies. The young dragon-flies (fig. 59) may be got by 
raking out some of the slime and aquatic vegetation from the bottom 
of a small pond. Compare the external structure of the adult dragon- 
flies with that of the grasshopper ; note the large eyes, the narrow 
nerve-veined wings, the biting mouth-parts, and the short antennae. 




Fig. 57. — A bird louse, Nir- 
mus prcestans, from a tern, 
Sterna maxima. Most birds 
are infested with small, 
wingless, biting insects, 
called bird -lice, which are 
external parasites feeding 
on the feathers of the bird 
host. The bird louse 
figured is about T ^ in. long. 
(Photo-micrograph by Geo. 
O. Mitchell.) 



BRANCH ARTHROPODA ; CLASS INSECT A : THE INSECTS *95 

Compare the young- dragon-flies with the adults ; note the devel- 
oping- wings and the peculiar modification of the lower lip into a 
protrusible, grasping organ which when at rest is folded like a mask 
over the face. Examine the interior of the posterior part of the 
alimentary canal to find the rectal gills. Obtain specimens of adult 
and young May-flies. The young may be found on the under side 
of stones in a " riffle " in almost any stream. They live also in ponds. 
They may be recognized by reference to fig. 61. Compare adult 
May-flies with the dragon-flies ; note the weakly chitinized, delicate 
body-wall, and the difference in size between fore and hind wings ; 
note the biting mouth-parts of the young and their absence or 
presence in vestigial condition only in the adults. 

The young of both dragon-flies and May-flies may easily be kept 
alive in the laboratory aquarium (fruit-jars or battery-jars with pond 
water in), and their feeding habits, their swimming, their respiration, 
and much of their development observed. The young May-flies 
should be got from ponds, not running streams. Put one ol these 
semi-transparent May-fly nymphs into a watch-glass of water, and 
examine under the microscope. The movements of the gills, heart, 
and alimentary canal, and much of the anatomy can be readily made 
out. The emergence of the adult from the nymphal skin can be 
seen if close watch is kept. The young dragon-flies may be seen to 
capture and devour their prey. They may also transform into adults, 
but for this it will be necessary to obtain nymphs nearly ready for 
transformation. 

Among the most familiar and interesting insects are the 
dragon-flies (fig. 58), sometimes called " devil's darning- 
needles.' They are commonly seen flying swiftly about 
over ponds or streams catching other flying insects. The 
dragon-flies are the insect-hawks ; they are predaceous and 
very voracious, and are probably the most expert flyers 
of all insects. There are many species, and their bright 
iridescent colors and striking wing-patterns make them 
very beautiful. The young dragon-flies (fig. 59) are 
aquatic, living in streams and ponds, where they feed 
on the other aquatic insects in their neighborhood. 
They catch their prey by lying in wait until an insect 
comes close enough to be reached by the extraordi- 
narily developed protrusible grasping lower lip (fig. 60). 
When at rest this lower lip lies folded on the face so as 
to conceal the great jaws. The young dragon-flies breathe 



196 



ELEMENTARY ZOOLOGY 



by means of gills which do not project from the outside 
of the body, as do the gills of other aquatic insects, but 
line the inner wall of the posterior or rectal part of the 




Fig. 58. — A dragon fly. Sympeti'um Fig. 59. — The young (nymph) of the 
illotimi, common in California. dragon-fly, Sympetmm illotum. 
(From life.) (From Jenkins and Kellogg.) 

alimentary canal. Water enters the canal through the 
anal opening and bathes these gills, bringing oxygen to 
them and taking away carbonic acid gas. The aquatic 





Fig. 60. — Young (nymph) dragon-fly, showing lower lip folded and ex- 
tended. (From Jenkins and Kellogg.) 

immature life of the dragon-flies lasts from a few months 
to two years. When ready to change to adult, the young 
crawls out of the water and clinging to a rock or plant 
makes its last molt. 



BRANCH ARTHROPOD A; CLASS INSECT A : THE INSECTS 197 



Other abundant and interesting pond and brook insects 
are the May-flies. The young May-flies (fig. 61) are 
aquatic, living in streams and 
ponds and feeding on minute 
organisms such as diatoms and 
other algae. The immature life 
lasts a year, or even two or three 
in some species, and then the 



May-fly crawls out of the water 
upon a plant-stem or projecting 
rock and, molting, appears as the 
winged adult. The adult May- 
fly, having its mouth-parts atro- 
phied (a few May-flies have func- 
tional mouth-parts), takes no food, 
and lives only a few hours or at 
most perhaps a few days. It has 
the shortest life (in adult stage) 
of all insects. The female drops 
her eggs into the water. 

Hemiptera: the sucking-bugs. 

— Technical Note. — Obtain speci- 
mens of water-striders (narrow elongate-bodied insects with long 
spider-like legs which run quickly about on the surface of ponds 
or quiet pools in streams), water-boatmen (mottled grayish insects 
about half an inch long which swim and dive about in ponds and 
stream-pools), back-swimmers (which are usually in company with 
the water-boatmen, but which swim with back downwards and 
are marked with purplish-black and creamy white patches), cicadas 
(the dog-day locusts), and plant-lice (the " green fly "of rose-bushes 
and other cultivated plants). Compare the external structure of 
some of these Hemiptera with the other insects already examined ; 
note especially the sucking beak, composed of the elongate tube- 
like labium in which lie the greatly modified flexible needle-like 
maxillse and mandibles, the whole forming an equipment for pierc- 
ing and sucking. Obtain immature specimens of some of these 
insects (distinguished by their smaller size and the wing-pads) ; note 
that the metamorphosis is incomplete, the young resembling the 
parents in general appearance. Both immature and adult specimens 
of water-boatmen (Corisa), back-swimmers {Notonecta) y and water- 




Fig. 61. — Young (nymph) of 
May-fly, showing (g) tra- 
cheal gills. (From Jenkins 
and Kellogg.) 



198 



ELEMENTARY ZOOLOGY 



striders (Hygrotrechus) can be easily kept in the laboratory aquaria- 
and their swimming, breathing, and feeding habits observed. Note 
especially the carrying of air down beneath the water. 

The Hemiptera are characterized particularly by their 
highly specialized sucking mouth-parts, no other of the 
sucking insects having the proboscis composed in the 





Fig. 62. — The female red orange scale 
insect, Aspidiotus aurantii, very injuri- 
ous to orange-trees. It has no wings, 
legs, nor eyes, but remains motionless 
on a leaf, stem, or fruit, holding fast by 
its long slender beak, through which it 
sucks up the plant-sap. The male is 
winged, and has no mouth-parts, taking 
no food. (Photo-micrograph by Geo. 
O. Mitchell.) 



Fig. 63. — The female rose- 
scale, Diaspis roses, a 
pest of rose-bushes, with- 
out eyes, wings, or legs, 
but with slender sucking 
proboscis. The male is 
winged and without 
mouth-parts. (Photo-mi- 
crograph by Geo. O. 
Mitchell.), 



same manner. The palpi of both maxillae and labium 
are wholly wanting in Hemiptera and the flexible needle- 
like maxillae and mandibles are enclosed in the tubular 
labium. This order is a large one and includes many 
well-known injurious species, as the chinch-bug (Blissus 
lencopterus), which occurs in immense numbers in the 
grain-fields of the Mississippi valley, sucking the juices 
from the leaves of corn and wheat, the grape Phylloxera 
{Phylloxera vastatrix), so destructive to the vines of 
Europe and California, the scale insects (Coccidce) (figs. 



BRANCH ARTHROPODS ; CLASS INSECT A : THE INSECTS 199 



62 and 63), the worst insect, pests of oranges, the squash- 
bugs and cabbage-bug and a host of others. Some of 
the Hemiptera, for example, the lice and bed-bugs, are 
predaceous, sucking the blood of other animals. 

The water-striders (fig. 64) catch other insects, both 
those that live in the water 
and those which fall on to 
its surface, and holding the 
prey with their seizing 
fore legs they pierce its 
body with their sharp 
beak and suck its blood. 
They lay their eggs in the 
spring glued fast to water- 
plants. The young water- 
striders are shorter and 
stouter in shape than the 
adults. 

The water-boatmen 
(fig. 65) and back-swim- 
mers swim and dive about in the water, 
or less frequently to the surface to get a supply of air. 

This air they hold under the 
wings, or on the sides and 
under part of the body en- 
tangled in the fine hairs on 
the surface. The insects 
appear to have silvery spots 
on the body, due to the 
presence of this air. The 
1 ' rowi'ng ' ' legs of the water- 
boatmen {Coins a) are the 
hindmost pair; in the back-swimmers {Notonecta) they 
are the middle legs. 

The cicadas (fig. 66) are the familiar insects of summer 




Fig. 64. — A water-strider, Hygrotrechns 
sp. (From Jenkins and Kellogg.) 



coming more 




Fig. 65. — A water-boatman, Corisa 
sp. (From Jenkins and Kellogg.) 



200 



ELEMENTARY ZOOLOGY 




*& 




which sing so shrilly from the trees, the seventeen-year 
cicada (Cicada septendecivi) (oftentimes called locust) 

being the best known of 
this family. Its eggs 
are laid in slits cut by 
the female in live twigs. 
The young, which hatch 
in about six weeks, do 
not feed on the green 
foliage, but fall to the 
ground, burrow down to 
the roots of the tree and 
there live, sucking the 
juices from the roots, for 

Fig. 66. — The seventeen -year cicada, Ci- sixteen years and ten or 

cada septendecim ; the specimen at left i r \\TU 

showing sound -making organ, v. p., ven- eieven months. When 

tral plate; *, tympanum. (From speci- about to become adult, 

men.) - • i 1 

the young cicada crawls 
up out of the ground and clinging to the tree-trunk molts 
for the last time, and flies to the tree-tops. 

The plant-lice {Aphididce) are small soft-bodied 
Hemiptera which have both winged and wingless indi- 
viduals. In the early spring a wingless female hatches 
from an egg which, laid in the preceding fall, has passed 
the winter in slow development. This wingless female, 
called the stem-mother, lays unfertilized eggs or more 
often perhaps gives birth to live young, all of which are 
similarly wingless females which reproduce partheno- 
genetically. This reproduction goes on so rapidly that 
the plant-lice become overcrowded on the food-plant and 
then a generation of winged * individuals is produced from 

* It has been shown by experiment that the winged individuals, which are 
able to leave the old food-plant and scatter over new plants, do not appear 
until the food-supply begins to run short. At the insectary of Cornell Uni- 
versity ninety -four successive generations of wingless individuals were bred, 



BRANCH ARTHROPODA ; CLASS INSECT A : THE INSECTS 201 

time to time. These winged plant-lice fly away to new 
plants. In the autumn a generation of males and females 
is produced ; these individuals mate and each female lays 
a single large egg which goes over the winter, and pro- 
duces in the spring the wingless agamic stem-mother. 
Plant-lice produce honey-dew, a sweetish substance much 
liked by ants, and the lice are often visited, and sometimes 
specially cared for, by the ants for the sake of this honey- 
dew. Small as they are, plant-lice occur in such numbers 
as to do great damage to the plants on which they feed. 
The apple-aphis, cherry-aphis, pear-aphis, cabbage-aphis 
and others are well-known pests. The most notoriously 
destructive plant-louse is the grape Phylloxera, which 
lives on the roots and leaves of the grape-vine. Im- 
mense losses have been caused by this pest, especially in 
the wine-producing countries of southern Europe. 

Diptera : the flies, — Technical Note. — Obtain specimens 
of the adult and young stages of the blowfly and the mosquito. All 
the young stages of the blowfly may be obtained, and its life-history 
studied, by exposing a piece of meat to decay in an open glass jar. 
The larvae of the mosquito are the familiar wrigglers of puddles 
and ponds, and by collecting some of them and keeping them in a 
glass jar of water covered with a bit of mosquito-netting, the life- 
history of the mosquito is easily studied. If the eggs can be ob- 
tained from the pond so much the better ; they are in little black 
masses floating on the surface of the water, and resemble at first 
glance nothing so much as a floating bit of soot. The external 
structure of the adult flies should be compared with that of the 
other insects studied, noting especially the condition of mouth-parts 
and wings, and the substitution of balancers for the hind wings. 
The mouth-parts of the mosquito are in the form of a long proboscis 
composed of six slender needle-like stylets lying in a tube narrowly 
open along its dorsal surface. The tube is the labium, and the 
stylets are the two maxillae, two mandibles, and two other parts 
known as the epipharynx and the hypopharynx. Two additional 
thicker elongate segmented processes lying outside of and parallel 
with the tube are the maxillary palpi. The male mosquito (distin- 
guished from the female by the more hairy or bushier antennae) lacks 

by taking care to provide a constantly abundant supply of food. This ex- 
periment was continued for more than four years. 



202 ELEMENTARY ZOOLOGY 

the pair of neeclle-like mandibles. The mouth-parts of the blowfly 
are composed almost exclusively of the thick fleshy proboscis-like 
labium, which is expanded at the tip to form a rasping organ 

The Diptera or true flies are readily distinguishable 
from other insects by their having a single pair of wings 
instead of two pairs, the hind wings being transformed 
into small knob-headed pedicels called balancers or 
halteres. The flies undergo complete metamorphosis, 
and their mouth-parts are fitted for piercing and sucking 
(as in the mosquito) or for rasping and lapping (as in the 
blowfly). Nearly 50,000 species of flies are known, more 
than 4,000 being known in North America alone. 

The blowfly {Calliphora vomitoria) is common in 
houses, but can be distinguished from the house-fly by its 
larger size and its steel-blue abdomen. It lays its eggs 
on decaying meat (or other organic matter) and the white 
footless larvae (maggots) hatch in about twenty-four 
hours. They feed voraciously and become full grown in 
a few days. They then change into pupae which are 
brown and seed-like, being completely enclosed in a uni- 
form chitinized case w r hich wholly conceals the form of the 
developing fly. The house-fly has a life-history and im- 
mature stages like the blowfly, but its eggs are deposited 
on manure. 

The mosquito {Ciilex sp.) (fig. 6j) lays its eggs in a 
sooty-black little boat-shaped mass which floats lightly on 
the surface of the water. In a few days the larvae, or 
"wrigglers," issue and swim about vigorously by bend- 
ing the body. The head end of the body is much broader 
than the other, the thoracic segments being markedly 
larger than the abdominal ones. The head bears a pair 
of vibrating tufts of hairs, which set up currents of air that 
bring microscopic organic particles in the water into the 
wriggler's mouth. At the posterior tip of the body are 
two projections, one the breathing-tube (the wriggler 



BRANCH ARTHROPODA; CLASS INSECT A : THE INSECTS 203 

coming often to the surface to breathe), and the other 
the real tip of the abdomen. The wriggler, although 
heavier than water, can hang suspended from the surface 
film by the tip of its breathing-tube. It changes in a few 




Fig. 67. — The mosquito, Culex sp. ; showing eggs (on surface of water), 
larvae (long and slender, in water), pupa (large headed, at surface), 
and adult (in air). (From living specimens.) 

days into the pupa, which, instead of being quiescent as 
with most flies, can swim about. It has a large bulbous 
head end and the posterior end of the body bears a pair 
of swimming-flaps. It takes no food. When ready to 



204 



ELEMENTARY ZOOLOGY 



change to the adult mosquito the pupa (which, unlike the 
wriggler, is lighter than water) floats at the surface of the 
water, back uppermost. The chitinous cuticle splits 
along the back and the delicate mosquito comes out, rests 





Fig. 68. — The house-flea, Pulex irritans; a, larva; d, pupa; c, adult. 
(The fleas are probably more nearly related to the Diptera than to any 
other order of insects. (After Beneden.) 



on the floating pupal skin until its wings are dry, and 
then flies away. Only the female mosquitoes suck blood. 
If they cannot find animals, mosquitoes live on the juices 
of plants. They are world-wide in their distribution, 
being serious pests even in Arctic regions, where they are 
often intolerably numerous and greedy. Recent investi- 
gations have shown that the germs which cause malaria 
in man live also in the bodies of mosquitoes, and are in- 
troduced into the blood of human beings by the biting 



BRANCH ARTHROPODS ; CLASS INSECT A : THE INSECTS 205 

(piercing) of the mosquitoes. It is probable also that the 
germs of yellow fever are distributed by mosquitoes in the 
same way. By pouring a little kerosene on the surface 
of a puddle no mosquitoes will be able to escape from 
the water. 



Lepidoptera : the moths and butterflies. — Technical 

Note. — Obtain specimens of a few moths, and compare with the 
butterfly already studied ; note especially the character of antennae. 
Obtain miscellaneous specimens of larvae, pupae, and cocoons of any 
moths or butterflies. Note the variety in colors, markings, and 
skin coverings of the larvae ; note the shape and markings of the 
pupae. Rear from eggs, larvae, or pupae in breeding-cages any 
moths and butterflies obtainable (for directions for rearing moths 
and butterflies see Chapter XXXIY), keeping note of the times of 
molting and of the duration of the various immature stages. If 
the eggs of silkworms can be obtained the whole life cycle of the 
silkworm moth can be observed in the schoolroom. The larvae 
(worms) feed on mulberry or osage orange leaves, feeding vora- 
ciously, growing rapidly and making no attempts to escape. The 
molting of the larvae can be observed, the spinning of the silken 
cocoon, and the final emergence of the moth. The moths after 
emergence will not fly away, but if put on a bit of cloth will mate, 
and lay their eggs on it. From these eggs, which should be kept 
well aired and dry, larvae will hatch in nine or ten months (if the 
race is an " annual "). 



The Lepidoptera (figs. 69-74) include all those insects 
familiarly known to us as moths and butterflies ; they are 
characterized by their scale-covered wings (fig. 69) and 
long nectar-sucking proboscis composed of the two inter- 
locking maxillae. They undergo a complete metamorpho- 
sis (fig. 70) and their larvae are the familiar caterpillars of 
garden and field. These larvae have biting mouth-parts 
and feed on vegetation, some of them being very injurious, 
for example the army-worms, cut-worms, codlin moth 
worms, etc. The adult moths and butterflies take only 
liquid food, or no food at all, and are wholly harmless to 
vegetation. The structure and life-history of a butterfly 
has already been studied, and in the more general condi- 



206 



ELEMENTARY ZOOLOGY 



tions of structure and life-history there is much similarity 
in the many insects of this order. The eggs are usually 
laid on the food-plant of the larva ; the larva feeds on the 




Fig. 69. — A small, partly denuded part, much magnified, of a wing of a 
" blue" butterfly, Lyccena sp., showing the wing, scales and the pits in 
the wing- membrane, in which the tiny stems of the scales are inserted. 
(Photo-micrograph by Geo. O. Mitchell.) 



leaves of this plant, grows, molts several times, and 
pupates either in the ground or in a silken cocoon or 
simply attached to a branch or leaf. There are about 
six thousand species of moths and butterflies known 
in North America, and they are our most beautiful in- 
sects. 



Coleoptera: the beetles. — Technical Note. — Obtain 
specimens of various beetles, among them some water-beetles and 
June-beetles with their young stages, if possible ; if not, then the 
young stages and adults of any beetle common in the neighborhood 
of the school. Of the swimming and diving water-beetles there are 
three families, viz., the Gyrinidae or whirligig beetles, with four eyes 
(each compound eye divided in two), the Hydrophilidae, or water- 
scavengers with two eyes and antennas with the terminal segments 



BRANCH ARTHRQPODA ; CLASS INSECTA : THE INSECTS 207 

thicker than the others, and the Dytiscidae or predaceous water- 
beetles with two eyes and slender thread-like antennae. Try to 
find Dytiscidae, large, oval, shining black beetles ; the larvae are 
called water-tigers and are long, slim, active creatures with six legs 




Fig. 70. — The forest tent-caterpillar moth, Clisiocampa dissti-ia. in its 
Various stages; ///. male moth; /, female moth; p, pupa; e, eggs (in a 
ring) recently laid; g. eggs hatched; c, larva or caterpillar. Moths 
and caterpillar are natural size, eggs and pupa slightly enlarged. 
(Photograph by M. V. Slingerland. ) 



and slender curving jaws (see fig. 76). The June-beetles are the 
heavy brown buzzing " June-bugs " and their larvae are the common 
"white grubs "found underground in lawns and pastures. Have 
live water-tigers and predaceous water-beetles in the aquarium. 
Note their feeding and breathing. Compare the external structure 
of the beetles with that of the other insects, noting especially the 
biting mouth-parts, and their thickened horny fore wings serving 
as covers for the folded membranous hind wings. 



208 



ELEMENTARY ZOOLOGY 



The Coleoptera is the largest insect order, probably 
100,000 species of beetles being known, of which 10,000 




Fig. 71. — A trio of apple tent-caterpillars, Clisiocampa americana, natural 
size. These caterpillars make the large unsightly webs or i; tents " in 
apple-trees, a colony of the caterpillars living in each tent. (Photograph 
from life by M. V. Slingerland.) 

species are found in North America. They pass through 
a complete metamorphosis (figs. 75 and 76), the larvae of 
the various kinds showing much variety in form and habit. 



BRANCH ARTHROPODA ; CLASS INSECT A : THE INSECTS 209 



The pupse are quiescent and are mummy-like in appear- 
ance, the legs and wings being folded and pressed to the 
ventral surface of the body. Among the familiar beetles 
are the lady-birds, which are beneficial insects feeding on 
plant-lice and other noxious forms; the beautifully colored 




Fig. 72.— -A. family of forest tent-caterpillars {Clisiocampa dis stria , resting 
during the day on the bark, about one-third natural size. (Photograph 
from life by M. V. Slingerland.) 

tiger-beetles, predaceous in habit; the "tumblebugs " and 
carrion beetles, which feed on decaying organic matter; 
the luminous fire-flies with their phosphorescent organs 
on the ventral part of the abdomen; the striped Colorado 
potato-beetle and the cucumber-beetles and numerous 
other destructive leaf-eating kinds; the various weevils 



2IO 



ELEMENTARY ZOOLOGY 



(fig. 78) that bore into fruits, nuts and grains, and the 
many wood-boring beetles, destructive to fruit-trees as 
well as to shade- and forest-trees. 

The predaceous water-beetles {Dytictis sp.) are common 
in ponds and quiet pools in streams. When at rest they 
hang head downward with the tip of the abdomen just 
projecting from the water. Air is taken under the tips of 




Fig. 7 ? > — Moths of the peach-tree borer, Sanninoidea exitiosa, natural size; 
the upper one and the one at the right are females. (Photograph by 
M. V. Slingerland.) 

the folded wing-covers (elytra) and accumulates so that 
it can be breathed while the beetle swims and feeds under 
water. When the air becomes impure the beetle rises to 
the surface, forces it out, and accumulates a fresh supply. 
The beetles are very voracious, feeding on other insects, 
and even on small fish. The eggs are laid promiscuously in 
the water, and the elongate spindle-form larvae (fig. yj) 




Fig. 74. — Army- worms, larvae of the moth, Lencania tmipimcta, on corn. 
(Photograph by M. V. Slingerland.) 



212 



ELEMENTARY ZOOLOGY 



called water-tigers are also predaceous. They suck the 
blood from other insects through their sharp-pointed 

sickle-shaped hollow 
mandibles. When a larva 
is fully grown it leaves 
the water, burrows in 
the ground, and makes a 
round cell within which it 
undergoes its transforma- 
tions. The pupa state 
lasts about three weeks 
in summer, but the larvae 
that transform in autumn 
remain in the pupa state 
all winter. 

The June-beetles (June- 
bugs) (Lachnosterna sp.) 
feed on the foliage of 
„ ™, . ,. , , lM trees. Their eges are 

Fig. 75. — The qumce-curcuho (a beetle), ^^ 

Conotrachelus cratcegi* natural size and laid among the roots of 

SliS d a„d.) (Ph0t0gl ' aPh ^ M ' V - £™ SS in Httle h0ll0W balls 

of earth, and the fat slug- 
gish white larvae feed on the grass-roots. They some- 
times occur in such numbers as to injure seriously lawns 
and meadows. The larvae live three years (probably) 
before pupating. They pupate underground in an earthen 
cell, from which the adult beetle crawls out and flies up 
to the tree-tops. 

Hymenoptera : the ichneumon flies, ants, wasps, and 

bees. — Technical Note. — Obtain specimens of wasps, both 
social (distinguished by having each wing folded longitudinally) and 
solitary (wings not folded longitudinally), and if possible of both 
queens (larger) and workers (smaller) of the social kinds ; of ants 
both winged (males or females) and wingless (workers) individ- 
uals ; also of honey-bees, including a queen, drones, and workers, 
and some brood comb containing eggs, larvae, and pupae. The bee 




BRANCH ARTHROPOD A ; CLASS INSECT A : THE INSECTS 213 

specimens can be got of a bee raiser. Compare the external struc- 
ture of ants, bees, and wasps with that of other insects ; note the 
pronounced division of the body into three regions (head, thorax, 
abdomen) ; note the character of the mouth-parts having mandibles 
fitted for biting (ants and wasps) or moulding wax (honey-bees) and 
having the other parts adapted for taking both solid and liquid 
food ; note the sting (possessed by the females and workers only). 
Observe the behavior of bees in and about a hive ; note the coming 
and going of workers for food. Observe bees collecting pollen at 
flowers ; observe them drinking nectar. Examine the honey-bee 





Fig. 76. — Immature stages of the quince curculio, Conotrachelus cratcegi; 
at the left, the larva natural size and enlarged; at the right, the pupa. 
The beetle lays its eggs in pits on quinces, and the larva lives inside 
the quince as a grub; the pupa lives in the ground. (Photograph by 
M. V. Slingerland.) 

in its various stages, tgg, larva, pupa, adult. Note the special 
structure of the adult worker fitting it to perform its various special 
labors ; the pollen-baskets on the hind legs ; the w T ax-plates on the 
ventral surface of the abdomen, the wax-shears between tibia and 
tarsus of hind legs ; the antennae-cleaners on the fore legs ; the 
hooks on front margin of hind wings, etc. 



The Hymenoptera include the familiar ants, bees, and 
wasps, and also a host of other four-winged, mostly 
small, insects, many of which are parasites in their larval 
stage on other insects. All Hymenoptera have a com- 



2T4 



ELEMENTARY ZOOLOGY 



r%. 




plete metamorphosis, and their habits and instincts are, 
as a rule, very highly specialized. The parasitic Hymen- 

optera such as the ichneumon flies, 
chalcid flies, etc., are stingless but 
have usually a piercing ovipositor 
(the sting being only a modified 
ovipositor). The general life-history 
of these ichneumons is as follows: 
the female ichneumon fly, finding 
one of the caterpillars or fly or beetle 
larvae which is its host, settles on it 
and either lays an egg or several 
eggs on it, or thrusting in its ovi- 
positor, lays the eggs in the body; 
the young ichneumon hatching as 
a grub burrows into the body of its 
caterpillar host, feeding on the body- 
tissues, but not attacking the heart 
Fig. 77. -Water-tiger, the or nervous system, so that the host 

larva 01 the predaceous J 

water-beetle, Dyticus sp. is not soon killed; the ichneumon 
(From specimen.) pupa tes either inside the host, or 

crawls out and, spinning a little silken cocoon (fig. 160), 

pupates on the surface of the 

body or elsewhere. 

Some of the stingless Hymen- 

optera are not parasites, but are 

gall-producers. The female with 

its piercing ovipositor lays an 

egg in the soft tissue of a leaf or Fig. 78.— The plum curculio, 

Stem, and after the larva hatches Conotrachelus nenuphar a 

beetle very injurious to plums. 

the gall rapidly forms. The (Photograph by M. V. Sim- 
larval insect lies in the plant- an °* 
tissue, having for food the sap which comes to the rapidly 
growing gall. It pupates in the gall, and when adult 
eats its way out. 




BRANCH ARTHROPODA ; CLASS INSECT A : THE INSECTS 215 

The ants, bees, and wasps are called the stinging 
Hymenoptera, although the ants we have in North 
America have their sting so reduced as to be no longer 
usable. Among these Hymenoptera are the social or 
communal insects, viz., all the ants, the bumblebees and 
honey-bee, and the few social wasps, as the yellow-jacket 




Fig. 79. — The currant- stem girdler, Janus integer, a Hymenopteron at 
work girdling a stem after having deposited an egg in the stem half an 
inch lower down. (Photograph by M. V. Slingerland.) 

and black hornet. There are many more species of non- 
social or solitary bees and wasps than social ones, and 
their habits and instincts are nearly as remarkable. 

The solitary and digger wasps do not live in com- 
munities as the hornets do, but each female makes a nest 
or several nests of her own, lays eggs and provides for 



216 ELEMENTARY ZOOLOGY 

her own young. The nest is usually a short vertical or 
inclined burrow in the ground, with the bottom enlarged 
to form a cell or chamber. In this chamber a single egg 
is laid, and some insects or spiders, captured and so stung 
by the wasps as to be paralyzed but not killed, are put in 
for food. The nest is then closed up by the female, 
and the larva hatching from the egg feeds on the enclosed 
helpless insects until full grown, when it pupates in the cell 
and the issuing adult gnaws and pushes its way out of the 
ground. Each species of wasp has habits peculiar to itself, 
making always the same kind of nest, and providing 
always the same kind of food. Some of these wasps make 
their nests in twigs of various plants, especially those with 
pithy centres in the stems. For interesting accounts of 
the habits of several digger wasps see Peckham's " The 
Solitary Wasps. 

The solitary bees, of which there are similarly many 
kinds, are like the solitary w r asps in general habit, only 
they provision the nest with a mixture of pollen and nectar 
got from flowers instead of with stung insects. Some- 
times many individuals of a single species of solitary bee 
will make their nests near together and thus form a sort 
of community in which, however, each member has its 
own nest and rears its own young. In the case of certain 
small mining bees of the genus Halictus, a step farther 
toward true communal life is taken by the common build- 
ing and use by several females of a single vertical tunnel 
or burrow from which each female makes an individual 
lateral tunnel, at the end of which is a brood-chamber. 
Perhaps half a dozen females will thus live together, each 
independent except for the common use of the vertical 
tunnel and exit. 

The bumblebees {Bombus sp.) are truly communal in 
habit. All the eggs are laid by a queen or fertile female, 
which is the only member of the colony to live through 



BRANCH ARTHROPODA ; CLASS INSECT A : THE INSECTS 217 

the winter. In the spring she finds a deserted mouse's 
nest or other hole in the ground, gathers a mass of pollen 
and lays some eggs on it. The larvae, hatching, feed on 
the pollen, dig out irregular cells for themselves in it, 
pupate, and soon issue as workers, or infertile females. 
These workers gather more pollen, the queen lays more 
eggs, and several successive broods of workers are pro- 
duced. Finally late in the summer a brood containing 
males (drones) and fertile females (queens) is produced, 
mating takes place, and then before winter all the workers 
and drones and some of the queens die, leaving a few 
fertilized queens to hibernate and establish new communi- 
ties in the spring. 

The yellow 7 -jackets and hornets (Vespidae), the so- 
called social wasps, have a life-history very like that of 
the bumblebees. The communities of the social wasps 
are larger and their nests are often made above ground, 
being composed of several combs one above the other 
and all enclosed in a many-layered covering sac open 
only by a small hole at the bottom. This kind of nest 
hangs from the branch of a tree and is built of wasp-paper, 
which is a pulp made from bits of old wood chewed 
by the workers. The brood-cells are provisioned with 
killed and chewed insects, the larvae of both solitary and 
social w r asps being given animal food, while the larvae 
of both solitary and social bees are fed flower-pollen and 
honey. As in the bumblebees, all the members of the 
community except a few fertilized females die in the 
autumn, the surviving queens founding new colonies in 
the spring. The queen builds a miniature "hornet's 
nest ' ' in the spring, lays an egg in each cell and stores 
the cells with chewed insects. The first brood is com- 
posed of workers, which enlarge the nest, get more food, 
and relieve the queen of all labor except that of egg- 
laying. More broods of workers follow until the fall 



2l8 



ELEMENTARY ZOOLOGY 



brood of males and females appears, after which the 
original process is repeated. 

The honey-bees and ants show a highly specialized 
communal life, with a well-marked division of labor and 
an individual sacrifice of independence and personal 
advantage which is remarkable. Their communities are 
large, including thousands of individuals, and the struc- 
tural differences among the males, females, and workers 
are readily recognizable. With the ants the workers may 
be of two or more sorts, a distinction into large and small 
workers or worker majors and worker minors being not 
uncommon. 

A honey-bee community, living in hollow tree or hive, 
includes a queen or fertile female, a few hundred drones 
or fertile males, and ten to forty thousand workers, in- 
fertile females (fig. 80). The number of drones and 




Fig. 80. —The honey-bee, Apis mellifica ; A, queen, B, drone, C, worker. 

(From specimens.) 

workers varies, being smallest in winter. Each kind of 
individual has a certain particular part of the work of the 
whole community to do; the queen lays all the eggs, that 
is, is the mother of the entire community; the drones act 
simply as the royal consorts, fertilizing the eggs; while 
the workers build the comb, produce the wax from 
which the cells are constructed, bring in all the food con- 



BRANCH ARTHROPODA ; CLASS INSECT A : THE INSECTS 219 

sisting of flower-pollen and nectar, care for the young 
bees, fight off intruders, and in fact perform all the many- 
labors and industries of the community except those of 
reproduction. There is a certain not very well understood 
and perhaps not very sharply defined division of these 
labors among the worker individuals, the younger ones 
acting specially as " nurses," feeding and caring for the 
young bees (larvae and pupae), the older ones making the 
food-gathering expeditions. The queen lays her eggs one 
in each of many cells (fig. 81). These eggs hatch in three 
days, and the young bee appears as a white, soft, footless, 
helpless grub or larva that is fed at first by the nurses with 



t fv 



f 




1 



n 



^M^^m^wM 







mm 



W 

^ 



jtMP* 



Fig. 81. — Worker brood and queen cells of honey-bee ; beginning at the 
right end of upper row of cells and going to the left is a series of egg, 
young larvae, old larvae, pupa, and adult ready to issue ; the large 
curving cells below are queen cells. (From Benton.) 



a highly nutritious substance called bee-jelly which the 
nurses make in their stomachs and regurgitate for the 
larva. After two or three days of this feeding the larvae 
are fed pollen and honey. After a few days a small mass 
of this food is put into the cell, which is then " capped " 
or covered with wax. The larva after using up this food- 
supply pupates, and lies quiescent in the pupal stage for 



220 ELEMENTARY ZOOLOGY 

thirteen days, when the fully developed bee issues, and 
breaking through the wax cap of the cell is ready for the 
labors which are immediately assigned it. The bee with 
the kind of life-history just described is a worker. It has 
been demonstrated that the eggs which produce workers 
and those which produce queens do not differ, but if the 
workers desire to have a queen produced they tear down 
two or three cells around some one cell, enlarging this 
latter into a large vase-shaped cell. When the larva 
hatches from the Qgg in this cell it is fed for its whole 
larval life with bee-jelly. From the pupa into which this 
larva transforms issues not a worker but a new queen. 
The eggs which produce drones or males differ from those 
which produce queens and workers in being unfertilized, 
the queen having the power to lay either fertilized or 
unfertilized eggs. When a new queen appears or when 
several appear at once there is great excitement in the 
community. If several appear they fight among them- 
selves until only one survives. It is said that a queen 
never uses its sting except against another queen. The 
old queen now leaves the hive accompanied by many of 
the workers. She and her followers fly away together, 
finally alighting on some tree-branch and massing there 
in a dense swarm. This is the familiar act of "swarm- 
ing.' Scouts leave the swarm to find a new home, to 
which they finally conduct the whole swarm. Thus is 
founded a new colony. " This swarming of the honey- 
bee is essential to the continued existence of the species; 
for in social insects it is as necessary that the colonies be 
multiplied as it is that there should be a reproduction of 
individuals. Otherwise as the colonies were destroyed 
the species would become extinct. With the social wasps 
and with the bumblebees the old queen and the young 
ones remain together peacefully in the nest; but at the 
close of the season the nest is abandoned by all as an 



BRANCH ARTHROPODS ; CLASS INSECT A : THE INSECTS 221 

unfit place for passing the winter, and in the following 
spring each young queen founds a new colony. Thus 
there is a tendency towards a great multiplication of 
colonies. But with the honey-bee the habit of storing 
food for winter, and the nature of the habitations of these 
insects, render it possible for the colonies to exist in- 
definitely, and thus if the old and young queens remained 
together peacefully there would be no multiplication of 
colonies and the species would surely die out in time. 




Fig. 82. — Honey-bees building comb. (From Benton.) 

We see, therefore, that what appears to be merely 
jealousy on the part of the queen honey-bee is an instinct 
necessary to the continuance of the species.' 

For the special labors of gathering food, making wax, 
building cells, etc., the workers are provided with special 
structures, as the pollen-baskets on the outer surface 
of the widened tibia of the hind legs, the wax-shears 
between the tibia and first tarsal joint of the hind legs, 
the wax-plates on the ventral surface of the abdomen, 
etc. A great many interesting things connected with the 



222 



ELEMENTARY ZOOLOGY 



life and industries of a honey-bee community can be 
learned by the student from observation, using for a guide 
some book such as Cowan's 4 ' Natural History of the 
Honey-bee. " 

The gathering of food from long distances, the details 
of wax-making and comb-building, of honey-making (for 




Fig. 83. — Comb of the tiny East Indian honey-bee, Apis Jlorea, one-third 
natural size. (From Benton.) 

the nectar of flowers is made into honey by an interesting 
process), the storing of food, how the community protects 
itself from starvation when winter sets in or food is 
scarce by killing the useless drones and the immature 
bees in egg and larval stage, and many other phenomena 
of the life of the bee community present good opportuni- 
ties for careful observation and field study. Although 
the community is a persistent or continuous one, the indi- 
viduals do not live long, the workers hatched in the 
spring usually not more than two or three months, and 



BRANCH ARTHROPODA ; CLASS INSECT A: THE INSECTS 223 

those hatched in the fall not more than six or eight 
months. But new ones are hatching while the old ones 
are dying and the community as a whole always persists. 
A queen may live several years, perhaps as many as five. 
She lays about one million eggs a year. 

There are more than two thousand known species of 
ants (fig. 84), all of which live in communities and show a 
truly communal life. The ant workers are specially dis- 
tinguished in structure from the males and females by 
being wingless, and in numerous species there are two 
sizes or kinds of workers known as worker majors and 
worker minors. The life-history and communal habits of 
ants are not so thoroughly known as are those of the 
honey-bee, but they show even more remarkable speciali- 
zations. The ant nest or formicary is with most species an 
elaborate system of underground galleries and chambers, 
special rooms being used exclusively for certain special 
purposes, as nurse-rooms, food-storage rooms, etc. The 
food of ants comprises many animal and vegetable sub- 
stances, but the favorite food with many species is the 
4 'honey-dew' secreted by the plant-lice (Aphididae) 
and scale insects (Coccidae). To obtain this food an ant 
strokes one of the aphids with its antennae, when the fluid 
is excreted by the insect and drunk by the ant. In order 
to have a certain supply of this food some species of ants 
care for and defend these defenseless aphids, which have 
been called the "cattle' of the ants. In some cases 
they are even taken into the ants' nests and food provided 
for them. "In the Mississippi Valley a certain kind of 
plant-louse lives on the roots of corn. Its eggs are 
deposited in the ground in the autumn and hatch the fol- 
lowing spring before the corn is planted. Now the 
common little brown ant {Lasins flavits) lives abundantly 
in the cornfields, and is especially fond of the honey 
secreted by the corn-root louse. So when the plant-lice 



224 



ELEMENTARY ZOOLOGY 



hatch in the spring before there are corn-roots for them 
to feed on, the little brown ants with great solicitude 
carefully place the plant-lice on the roots of a certain 
kind of knot-weed which grows in the field and protect 
them until the corn germinates. Then the ants remove 
the plant-lice to the roots of the corn, their favorite food- 




Fig. 84. — The little black ant, Monomorhim minutitm; a, female, b, female 
with wings, c, male, d, workers, <?, pupa, f, larva, g, egg of worker, 
all enlarged. (From Marlatt.) 

plant. In the arid lands of New Mexico and Arizona the 
ants rear scale insects on the roots of cactus. ' 

The ants are among the most warlike of insects. 
Battles between communities of different species are 
numerous, and the victorious community takes possession 
of the food-stores of the conquered. Some species of ants 
live wholly by war and robbery. In the case of the 



BRANCH ARTHROPODS ; CLASS INSECT A : THE INSECTS 225 

remarkable robber-ant {Ecito?i), found in tropical and sub- 
tropical regions, most of the workers are soldiers, and no 
longer do any work but fighting. The whole community 
lives exclusively by pillage. Some kinds of ants go even 
farther than mere robbery of food-stores: they make 
slaves of the conquered ants. There are numerous species 
of these slave-making ants. They attack a nest of 
another species and carry into their own nest the eggs 
and larvae and pupae of the conquered community, and 
when these come to maturity they act as slaves of the 
victors, collecting food, building additions to the nest, 
and caring for the young of the slave-makers. 

As with the honey-bee the larval ants are helpless 
grubs and are cared for and fed by nurses. The so-called 
14 ants' eggs, " the little white oval masses which we often 
see being carried in the mouths of ants in and out of an 
ants' nest, are not eggs, but are the pupae which are 
being brought out to enjoy the warmth and light of the 
sun or being taken back into the nest afterward. 

There are in this country numerous species of ants 
showing much variety of habit and offering excellent 
opportunities for most interesting field observations. For 
an account of several of the common species see Corn- 
stock's " Manual of Insects," pp. 633-643. Ants may 
be readily kept in the schoolroom in an artificial nest or 
formicary and their life-history and habits closely watched. 
For full directions for making and keeping a simple and 
inexpensive formicary see Comstock's ''Insect Life," 
pp. 278-281. For an interesting account of some of the 
habits of the social insects see Lubbock's "Ants, Bees, 
and Wasps." 



26 



ELEMENTARY ZOOLOGY 



C 



m/ 



Class Myriapoda : The Myriapods, or Centipeds 

AND MlLLIPEDS. 

Belonging to the branch Arthropoda, with the classes 
Crustacea and Insecta, are three other classes, of which 
one, the Onychophora, is represented by a single genus 
Peripatus (Fig. 85), of extremely interesting animals. 
However, as these animals are not found 
in the United States we cannot study 
them. The other two classes are the 
Myriapoda, including the centipeds and 
millipeds or thousand-legged worms, and 
the Arachnida, including the scorpions, 
spiders, mites, and ticks. All these 
animals are often spoken of as insects, 
but though related to them they are not 
true insects. 

Technical Note. — From under stones or 
logs obtain specimens of millipeds, or thousand- 
legged worms (large blackish, cylindrical, worm- 
like animals with each body-segment back of the 
fourth bearing two pairs of jointed legs) ; also 
specimens of centipeds or hundred-legged worms 
(flattened, usually brownish or pale worm-like 
animals with the body-segments bearing only one 
pair of legs each) in the same places. Examine 
the external structure ; note number of body- 
rings ; division into body-regions ; presence of 
antennae; character and number of eyes; charac- 
ter of mouth-parts ; character and arrangement 
of legs. In the centipeds the first pair of legs is 
modified to form a pair of poison-fangs. They appear to belong to 
the mouth-parts. The internal anatomy will be found to be, if 
examined, much like that of insects and can be studied from the 
account of the anatomy of the water-scavenger beetle and butterfly 
larva. Compare the Myriapods with the Hexapods or true insects. 
What are the points of resemblance ? what are the points of differ- 
ence ? 

The Myriapoda are land-animals breathing by means 
of tracheae like the insects. In them the body-segments 



Fig. 85. — Peripatus 
eiseni (Mexico). 
(From specimen.) 



BRANCH AR THRUPODA ; CLASS M YR1APODA : M YRIAPODS 227 



are nearly uniform in character with the exception of the 
head, which, as in the insects, bears the mouth-parts and 
antennae. There is no grouping of the body-segments 
into regions except as the head is opposed to the rest of 
the body. (In a few myriapods there are indications of 
a division of the hind body into thorax and abdomen.) 
The presence of true legs on all the 
segments of the hinder region of the 
body and the lack of the three-region 
division of the body are the principal 
external structural characteristics which 
distinguish myriapods from insects. The 
internal anatomy corresponds in general 
character with that of insects. 

The most familiar myriapods are the 
millipeds, and the lithobians and centi- 
peds. The millipeds are cylindrical in 
shape, have two pairs of legs on most 
of the body-segments and are vegetable 
feeders, though some may feed on dead 
animal matter. The galley-worms 

(Jithts) (fig. 86), large, blackish, cylin- 
drical millipeds found under stones and 
logs and leaves and in loose soil, are 
familiar forms. They crawl slowly and when disturbed 
curl up and emit a malodorous fluid. They can easily be 
kept alive in shallow glass vessels with a layer of earth in 
the bottom, and their habits and life-history may thus be 
studied. They should be fed sliced apples, green leaves, 
grass, strawberries, fresh ears of corn, etc. They are not 
poisonous and may be handled with impunity. They lay 
their eggs in little spherical cells or nests in the ground. 
An English species of which the life-history has been 
studied lays from 60 to 100 eggs at a time. The eggs 
of this species hatch in about twelve days. 




Fig. 86. — A galley- 
worm (milliped), 
Julus sp. (From 
specimen.) 



228 



ELEMENTARY ZOOLOGY 



The lithobians and centipeds are flattened and have 
but a single pair of legs on each body-ring. They are 
predaceous in habit, catching and killing insects, snails, 

earthworms, etc. They can 
run rapidly, and have the first 
pair of legs modified into a 
pair of poison-claws, which 
are bent forward so as to lie 
near the mouth. The com- 




Fig. 87. — The skein centi- 
ped, Scatigera forceps, nat- 
ural size, common in houses 
and conservatories. (From 
Marlatt. ) 




Fig. 88. — Acentiped, Scolo- 
pendra sp. (From speci- 
men.) 



mon " skein" centiped [Scutigera forceps) (fig. 87) is 
yellowish and has fifteen pairs of legs, long 40-segmented 
antennae, and nine large and six smaller dorsal segmental 



BRANCH ARTHROPODS ; CLASS ARACHNID A : SPIDERS 229 

plates. The true centipeds [Scolopendrd) (fig. 88) have 
twenty-one to twenty-three body-rings, each with a pair 
of legs, and the antennae have seventeen to twenty joints. 
They live in warm regions, some growing to be very 
large, as long as twelve inches or more. The " bite " or 
wound made by the poison-claws is fatal to insects and 
other small animals, their prey, and painful or even 
dangerous to man. The popular notion that a centiped 
" stings " with all of its feet is fallacious. It is recorded 
by Humboldt that centipeds are eaten by some of the 
South American Indians. 



Class Arachnida: The Scorpions, Spiders, Mites, 

and Ticks. 

Technical Note. — Obtain specimens of various spiders ; the 
running or hunting spiders may be found on the ground, especially 
under stones and boards, the web-makers on their snares. Get 
also spiders' " cocoons " (egg-sacs). Examine the external structure 
of the spider ; note the two body-regions ; the number and character 
of legs ; the absence of antennae ; the number and arrangement of 
the eyes (which are simple, not compound) ; the mouth-parts, espe- 
cially the large mandibles ; the spinnerets at the tip of the abdomen 
(examine a cut off spinneret under the microscope to see the spin- 
ning-tubes i ; note the breathing openings or spiracles on under side 
of abdomen. Obtain also a scorpion if possible, and some ticks and 
mites. Compare with the spiders and note that in the scorpion 
the body is plainly seen (especially in the abdomen) to be composed 
of segments. Note the extreme fusion of the segments and body- 
regions in the mites and ticks. The common red spider of hot- 
houses and gardens is a mite ; ticks may sometimes be found on 
dogs. Observe various kinds of spider-webs, and try to observe 
the process of web-making (this can be observed early in the morn- 
ing or about dusk) by one of the orb-weaving garden-spiders. 
Live spiders can be kept in the schoolroom and their feeding 
habits and perhaps web-making habits observed. 

The class Arachnida is composed of Arthropods whose 
body-segments are grouped into two regions, a cephalo- 
thorax bearing the mouth-parts, eyes, and legs, and an 
abdomen. The segments composing these two parts are 



23° 



ELEMENTARY ZOOLOGY 




so fused that, except in the scorpions, they are usually 

indistinguishable. There are no 
antennae, the eyes are simple, the 
mouth-parts fitted for biting, and 
there are four pairs of legs. In 
their internal anatomy the arach- 
nids show in some forms a pecu- 
liar modification of the respiratory 
organs, the tracheae being flat and 
leaf-like and massed together in a 
few groups rather than being tubular 
and ramifying through the body. 

The dorsal vessel or heart usu- 
ally has a few blood-vessels or 
arteries running from it. This class 
is divided into three orders, the 
Arthrogastra, or scorpions, the 
Acarina, * 
o r mites 

and ticks, and the Araneina, or 

spiders. 

The scorpions (fig. 89) have 

the posterior six segments of 

the abdomen much narrower 

than the seven anterior seg- 
ments and forming a tail which 

bears at its tip a poison-fang or 

sting. This sting is used to kill 

prey, insects and other small 

animals. The tail can be darted 

forwards over the body to strike 

prey which has been previously FlG< 

seized by the large pincer-like 

maxillary palpi. Scorpions are 

common in warm regions, about twenty species being 



Fig. 89. — A scorpion Cen- 
trums sp., from Cali- 
fornia. (From specimen.) 




-The cheese-mite, Ty- 
roglyphus szro, greatly en- 
larged. (After Berlese.) 



BRANCH ARTHROPODA , CLASS ARACHNID A : SPIDERS 231 

known in southern North America. Their sting though 
painful is not dangerous to man. The young are born 
alive and are carried about by the mother for some time 
after birth. 

The mites (figs. 90 and 91) and ticks (fig. 92) are 
mostly small obscure animals, which live more or less 
parasitically. The common red spider of house-plants 
as well as the sugar- and cheese-mites, the dreaded 




/ 

Fig. 91. — Bird mite, species undetermined, from the gnome-owl, Glauci- 
dium gnomus. (Photo-micrograph by Geo. O. Mitchell.) 

itch-mite and the chigger are familiar examples of these 
degraded arachnids, and the wood-ticks, dog- and 
chicken-ticks are common examples of the larger blood- 
sucking forms. The body in both mites and ticks is very 
compact, the two body-regions, cephalothorax and ab- 
domen, being closely fused. 

The spiders have the abdomen distinctly set off from the 
cephalothorax. The eyes (fig. 93) vary in number and 
arrangement, the mandibles are large, each being com- 
posed of two parts, a basal hair-covered part, the falx, and 
a terminal smooth, shining, slender, sharp-pointed part, 



2$2 



ELEMENTARY ZOOLOGY 



the fang, which is movably articulated with the falx 
(fig. 93). In the falx is a poison-sac from which poison 




Fig. 92. — The dog or wood tick, Dermacentoi' a?7ierica?ius male, the most 
common tick in the Northern States. (After Osborn.) 



flows through the hollow fang and out at its tip. The 

legs vary in relative length in different spiders, and each 

is made up of seven joints. The spinnerets 

(fig. 94), which are situated at the tip of the 

abdomen, are six in number (a few spiders 

have only four), and are like little short 

fingers. They have at their tips many fine 

Fig. 93.— The little spinning-tubes from each of which a 

eyes and jaws, ^ ne s jjk en thread issues when the spider is 

showing ialx L 

and fang of a spinning. These many fine threads fuse as 
spier. ( rom they issue to form a single strong cable or 

Jenkins and J <=> <=> 

Kellogg.) sometimes a flat rather broad band. The 

spinnerets are movable, and by their manipulation the 
desired kind of line is produced. The silk comes from 




BRANCH ARTHROPODA ; CLASS ARACHNIDA : SPIDERS 233 

many silk-glands in the abdomen, from each of which a 
fine duct runs to a spinning-tube. 

The spiders may be divided into two groups according 
to their habits, viz., the wandering or hunting spiders, 





Fig. 94. — The six spinner- 
ets (below) of a spider, 
with one spinneret en- 
larged (above) to show 
the spinning ''spools" 
or tubes. (From Jenkins 
and Kellogg.) 




Fig. 95. — A long-legged spider, 
Tetragnatha sp., on its web. 
(From life.) 



which do not spin webs to catch their prey, and the 
sedentary or web-weaving spiders, which spin snares to 
catch their prey. The wandering spiders can spin silk, 
however, and often do so to line their burrows, to make 
nests, or to make egg-sacs. 

The hairy tarantulas and the trap-door spiders of 
similar appearance are among the most interesting of 



234 



ELEMENTARY ZOOLOGY 



the hunting spiders. They live in vertical burrows or 
tunnels in the ground which are lined with silk, and which 
in the case of the trap-door spider are covered with a door 
or lid made of silk and soil. The top of this door is 




Fig. 96. — A running spider (Lycosidae;. (From life.) 

always covered with soil or bits of leaves or twigs so that 
it is nearly indistinguishable from the surface of the 
ground about it. When the nest is in ground covered 
with moss the spider covers the door with moss. The 




Fig. 97. — A female running spider (Lycosidse) carrying its egg-sac about 
attached to its spinnerets. (From Jenkins and Kellogg. ) 

tarantulas hunt at night and rest in the burrow in the 
daytime. They are very large, sometimes having an 
expanse of legs of 6 inches. 

The common, rather large swift black spiders found 



BRANCH ARTHROPOD A ; CLASS ARACHNIDA : SPIDERS 235 



under stones and boards are hunting spiders, belonging 
to the family Lycosidae and are called the running spiders 
(fig. 96J. The}' live in burrows in the ground, coming 
out to stalk and chase their prey. The eggs are laid in 
globular egg-sacs which are often carried about, attached 
to the spinnerets, by the female (fig. 97). The young 
spiderlings after hatching, in some species, climb on to 
the mother's back and are carried by her for some time. 
Other kinds of wandering or hunting spiders are the crab- 
spiders (Thomisidae) (fig. 98), which run sidewise or back- 
ward as well as forward, and the black and red, fierce- 





Fig. 98. — A crab-spider (Thomi- Fig. 99. — A jumping spider (Atti- 
sidae). (From Jenkin- and Kellogg. ) dae.j (From Jenkins and Kellogg.) 



eyed, stout-bodied little jumping spiders (Attidae) (fig. 99), 
which leap on their prey. 

The sedentary or web-weaving spiders are of various 
kinds. They may be grouped according to their spinning 
habits into cobweb weavers (Therididae), small slim- 
legged spiders which make the familiar unsymmetrical 
cobwebs of houses and outbuildings; funnel-web weavers 
Agalenidae), larger long-legged spiders of meadow and 
field which spin a flat or concave horizontal web in the 
grass with a silken tube leading down to the ground; 
the curled-thread weavers (Dictynidae), which use in addi- 
tion to the usual lines peculiar broad lines made of waved 
or curled threads in their irregular webs made in fence- 



236 ELEMENTARY ZOOLOGY 

corners and on plants ; and finally orb-weavers (Epeiridae) 
(fig. 100), the host of variously colored and patterned 
stout-bodied garden-spiders which spin the beautiful sym- 
metrical circular webs familiar to all (fig. 101). If a 
complete uninjured orb web be examined it will be found 
to consist of a small central hub either open or closed, 
from which run radii to the outer edges of the web. 
Around the hub is an open or free zone, and farther out 
a spiral zone, so called because a line running in close 




Fig. 100. — Argiope sp., a large orb- weaver (Epeiridae). (From Jenkins 

and Kellogg.) 



spiral turns fills in the space between the radii. This is 
the real prey-catching part of the snare, and the silken 
line here is sticky, while the radii and some other parts 
of the web are made of silk that is not sticky. The 
web is supported by strong foundation-lines, attached to 
leaves, stems, or whatever is firm in the neighborhood of 
the web. The spider either rests on the web, usually in 
the centre, or lies concealed in a nest or tent near at hand 
from which a special path-line runs to the centre of the 
web. The building of one of these orb webs is a great 



BRANCH ARTHRCPCDA ; CLASS ARACHNID A : SPIDERS 237 

work, and is done with extraordinary nicety of manipula- 
tion by the use of feet and spinnerets. For account of 



^^ 




Fig. ioi. — Spider and its web in a rose-bush. (Photograph from life by 
Cherry Kearton; from "Wild Life at Home," bv permission of Cassell 
&Co.). 



web-making, etc., see McCook's " American Spiders and 
their Spinning Work." 

The habits and instincts of spiders in connection with 
the care of the young, the building of webs and nests, 
ballooning by means of silken lines, the active stalking 
and catching of prey, etc., are very interesting and offer 



2 3 8 



ELEMENTARY ZOOLOGY 



a good field for independent observation and study by the 

student. 




Fi-G. 102. — The triangle spider, Hyptiotes sp. (California), with its web; the 
spider rests on the taut guy-line, with a loop of the line held between 
its fore and hind legs; when an insect gets into the web the spider 
loosens the hold of its hind feet on the guy-line, thus allowing the web 
to spring forward sharply and further entangle the prey. (From 
Jenkins and Kellogg.) 



CHAPTER XXII 
MOLLUSC A: THE MOLLUSCS 

THE FRESH-WATER MUSSEL {Unto sp.) 

Structure (fig. 103). — Technical Note. — The fresh-water or 
river mussel lives commonly in the streams and lakes or ponds in 
the United States. It frequents muddy or sandy bottoms. Speci- 
mens can often be secured with a long-handled rake from the shore 
or picked up in shallow streams with the hand. If possible to keep 
the animals alive until ready for use, some of their habits may be 
observed. Place them in a tub or trough with water and mud ; 
when they have settled themselves put some powdered carmine, 
starch, or similar substance in the water near them, and note the 
water-currents. 

Living mussels which have been placed in a dish with 
mud several inches deep and covered with water will be 
seen to travel in a definite direction. The end which is 
in front is the head end. Note the process of thrusting 
out and retracting the fleshy foot which extends between 
the two valves of the shell. Note that the two valves are 
held together along the upper, or dorsal, surface by a 
horny structure, the Jiinge-ligament. Note near the hinge- 
line a prominence {tunbd) in each valve from which ex- 
tends a series of concentric lines of growth. The umbo 
is the oldest part of the valve. Note at the lower edge 
of the valves a soft membrane with a fringe along its free 
border. This is the edge of the mantle-lobes, flaps of the 
body-wall which cover the body and which aid in the 
functions of respiration and nutrition. 

239 



240 ELEMENTARY ZOOLOGY 

Technical Note. — Specimens which are to be dissected should 
be killed by dropping them for a few seconds into warm water, when 
the muscles will relax enough so that a chip may be thrust between 
the valves. If specimens are to be kept for some time before dis- 
secting they should be preserved in alcohol or \% formalin. In a 
dead specimen carefully remove the left valve. This is accomplished 
by slipping in a thin knife-blade close to the inner edge of the left 
valve and carefully cutting the two large adductor muscles which 
bind the valves together. The dissection should be made under 
water. 

Before the removal of the valve, as just described, 
notice a portion of the mantle adhering to the inner face 
of the valve, along a line of attachment indicated by a 
crease. This is the pallial line. After the left valve has 
been removed, the mantle being carefully separated from 
it, note the large conical projections from the valves, the 
hinge teeth, which fit into each other. Note the large 
muscle impression just in front of the hinge-teeth; this is 
the point of attachment of the anterior adductor muscle, 
while just behind and adjoining it is the impression of the 
anterior retractor muscle. Note posterior to the adductor 
and below the retractor a small impression which affords 
attachment for the protractor muscles of the foot. At 
the other end of the valve, note the large impression of the 
posterior adductor muscle with the impression of the small 
posterior retractor muscle just above it. 

Technical Note. — Lift back the left mantle-lobe, thus exposing 
the body parts underneath. 

Note the projecting muscular foot, the movements of 
which are governed by the retractor and protractor 
muscles attached to the impressions just mentioned. 
Note a pair of flattened plate-like structures composed of 
thin, ribbed, membranous folds. These are the gills. 
Note just beneath the anterior adductor muscle a small 
opening leading into the soft visceral mass of the body. 
This is the mouth. Note near the mouth two pairs of 
plate-like structures much smaller than the gills. These 



MOLLUSCA: THE MOLLUSCS 241 

are the labial palpi, and it is by their action that food- 
particles which have been brought in with the water are 
conveyed to the mouth. Note at the posterior part of 
each mantle-lobe a fringed portion which, together with 
a corresponding part on the other side, forms the inhalant 
siphon. The cilia of the fringes carry water and food- 
particles into the space enclosed by the mantle- lobes ; 
this space is the mantle-cavity. After the food has been 
taken out and the water has passed through the finely 
striated gills it is collected in a common cavity which 
extends above the two sets of gills on each side. This 
space is called the supra-branchial cavity. This cavity 
is continuous posteriorly with a space between the right 
and left mantle-lobes, which is connected with the 
exterior by an opening above the inhalant siphon called 
the exhalant siphon. The function of the gills is partly 
to produce currents of water carrying the food to the 
mouth, and partly respiratory. The mantle is an impor- 
tant organ of respiration. 

Make a drawing showing the organs described. 

Technical Note. — Carefully cut away the mantle and gills 
from the leftside, and also the labial palpi, being careful not to dis- 
turb the visceral mass. 

Note two openings along the line where the gills and 
foot come together. The uppermost is the opening of the 
ureter giving exit to the excretion from the kidneys ; the 
lower is the opening of the duct from the reproductive 
organs and is called the genital aperture. The products 
from both of these organs are carried out through the 
exhalant siphon. 

Note that th? mouth leads by a short tube (oesophagus 
or gullet) into a large cavity, the stomach, which is sur- 
rounded by a greenish mass, the digestive gland. 

Technical Note. — Carefully cut the delicate covering of the 
dorsal portion of the visceral mass and expose a cavity. 



242 ELEMENTARY ZOOLOGY 

The cavity thus exposed is the pericardium. Note 
within the pericardium a long tube extending through it. 
This is a portion of the alimentary canal, the rectum, 
which opens posteriorly through the anus into the supra- 
branchial chamber. Note a muscular sac about the 
rectum midway of its course through the pericardium. 
This is the unpaired ventricle of the heart. Attached to 
each side of the ventricle are thin-walled sacs, the right 
and left auricles, which are entered by fine blood-vessels, 
the efferent branchial veins, from the right and left gills. 
The blood brought through these blood-vessels from the 
gills flows into the auricles and from them into the un- 
paired muscular ventricle, from which it is forced anteriorly 
and posteriorly through two main arteries, the anterior 
and posterior aortas, to all parts of the body. After 
bathing the body-tissues the blood is collected into a 
median longitudinal vein beneath the pericardium called 
the vena cava. From the vena cava the blood passes 
through the kidneys and gills to be returned at last to the 
heart. The mantle acts as an organ for the aeration of 
the blood, and the blood it receives or at least part of it 
passes directly back to the heart without passing through 
the kidneys and gills. 

Note the delicate membranous dark-colored sac on the 
floor of the pericardium, the kidneys or nepliridia. These 
are paired structures which appear as two U-shaped tubes 
lying side by side. Each consists of a lower portion with 
thick folded walls, the kidney proper, and an upper thin- 
walled portion, the ureter. The kidneys open internally 
through a pair of reno-pericardial openings into the peri- 
cardium, while the ureters communicate with the mantle- 
cavity by an opening on the side of the body beneath the 
gills as already mentioned. The kidneys are profusely 
supplied with fine blood-vessels and carry off the waste 
matter from the blood. 



MOLLUSC A: THE MOLLUSCS 243 

Beneath the posterior adductor muscles note a small 
white spider-shaped body, the more or less united visceral 
ganglia of the nervous system. Posteriorly these ganglia 
give off nerves to the mantle and gills, while anteriorly 
there proceed two nerves, the cerebro-visceral connectives, 
running forward, one on either side of the foot close to 
the visceral mass, to the cerebro-plenral ganglia, paired 
ganglia lying near the mouth. A delicate commissure 
running over the gullet connects these ganglia. 

Technical Note. — Cut away the skin and outer muscular layer 
from the left side of the foot. 

Note the large stomach-cavity, surrounded by the 
digestive gland. Trace the convolutions of the alimentary 
canal through the foot to the anal exit. Note in the 
anterior portion of the foot a fused pair of ganglia similar 
to the visceral ganglia. These are the pedal ganglia, 
which are connected by a pair of delicate commissures, 
the cerebro-pedal connectives, with the cerebro-pleural 
ganglia. Note the glandular tissue which fills the cavity 
of the foot and surrounds the loops of the alimentary 
canal. This is the reproductive organ, which has its exit 
Leneath the gills on each side of the foot. The sexes of 
the mussel are separate, but the reproductive organs are 
very similar. 

Life-history and habits. — The eggs (ova) of the female 
pass first into the supra-branchial chamber, whence, after 
being fertilized, they drop into the outer pair of gill- 
chambers. These outer gills serve as brood-pouches, and 
here it is that the embryonic stages are passed through. 
The embryo when ready to issue has a soft body enclosed 
in two triangular valves. At this stage it is called a 
glocliidinm. The glochidium on being discharged through 
the exhalant siphon of the parent falls to the bottom, 
where it remains for a time, when it attaches itself to some 



244 ELEMENTARY ZOOLOGY 

fish by the lower hook-like projections of the valves and 
leads a truly parasitic life for two months, after which it 
undergoes a metamorphosis and falls to the bottom again, 
there to begin an independent existence. Mussels often 
congregate in favorite mud or sand banks. Their food 
consists primarily of small organisms, both plants and 
animals, which are taken from the water entering the 
mantle-cavity. Mussels move about slowly over the 
muddy bottom of the stream by means of the muscular 
foot. 

OTHER MOLLUSCS. 

The branch Mollusca includes the fresh-water mussels, 
the clams, oysters, snails, and slugs, the cuttlefishes, and 
all that host of animals we call " shells " or shell-fish, which 
we know familiarly only by the shell which they make, 
live in, and leave at death to tell the tale of their exist- 
ence. Not all the molluscs, however, form shells, that 
is, external shells which serve as houses. The familiar 
slugs do not, nor do a number of ocean forms called 
nudibranchs, which are somewhat like the land-slugs, only 
much prettier and more attractive. All the cuttlefishes 
and octopi are also without the hard calcareous shell. 
But most of the molluscs are shell-bearing animals. The 
shell may be bivalved, as in the mussel and clam, or uni- 
valved, that is, composed of a single piece which may be 
spirally twisted, as with the snail, or otherwise curiously 
shaped. The variety in the form, colors, and markings 
of the shells indicates the great diversity among molluscs. 
Molluscs live on land, in fresh water and in the ocean. 
No depths of the ocean abysses are too great for the 
octopi, no coast but has its many shells, hardly a pond 
or stream is without its mussels and pond-snails, and in 
all regions the land-snails and slugs abound. 



MOLLUSCA : THE MOLLUSCS 245 

Body form and structure. — The molluscs are not to 
be mistaken for any other of the lower animals; they 
have a structure peculiarly their own. In them the body 
is not articulated or segmented as with the worms and 
arthropods, nor radiate as in the echinoderms, nor plant- 
like as with the sponges and polyps. Where the typical 
molluscan body is w T ell developed it is composed of four 
principal parts: a head, with the mouth, feelers, eyes, and 
other organs of special sense; a trunk containing the 
internal organs; a foot which is a thick muscular mass not 
at all foot- or leg-like in shape, but w 7 hich is the organ 
of locomotion by means of which the mollusc crawls ; and 
a mantle which is a fold of the skin enclosing most of the 
body and which produces the shell. Such a typical 
molluscan body is possessed by most of the snails. But 
in most of the other molluscs one or more of these four 
body-regions are so fused with some other region as to 
be indistinguishable. In the mussels and clams the head 
is not at all set off from the rest of the body, the cuttle- 
fishes and octopi have no foot, the slugs have no shell. In 
the case of some of the molluscs without external shell there 
are inside the body the rudiments or vestiges of a shell. 

With regard to the internal organs we note the constant 
presence of three pairs of ganglia, viz., the brain, lying 
above the pharynx, which sends nerves to the feelers, 
eyes, and auditory organs ; the pedal ganglion, which sends 
nerves to the foot, and the visceral ganglion, which sends 
nerves to the viscera. This is a condition of the nervous 
system characteristic of all molluscs. The heart is a well- 
developed pulsating sac in the upper part of the body 
composed of either two or three chambers, and there is a 
well-defined closed system of arteries and veins, specially 
complete in the cuttlefishes and octopi. This highly 
developed condition of the circulatory system also distin- 
guishes the molluscs from the other invertebrates. 



246 ELEMENTARY ZOOLOGY 

Development. — Reproduction among the molluscs is 
always sexual. Multiplication by budding or by the 
parthenogenetic production of eggs is not known to occur. 
The eggs are usually laid in a mass held together by a 
gelatinous substance. In most species the young mollusc 
on hatching from the egg does not resemble its parent, 
but is a free-swimming larva called a veliger. It is 
provided with cilia for organs of locomotion. It must 
undergo a radical change in order to reach the adult 
stage. Thus metamorphosis occurs in this branch as well 
as among the Arthropods and Echinoderms. In the 
development of some molluscs, however, there is little or 
no metamorphosis, the young being hatched in a condi- 
tion much resembling, except in size, the parent. 

Some of the special characteristics of structure, life- 
history, and habits of the molluscs will be noted in our 
consideration of the various kinds. 

Classification. — The branch Mollusca is divided into 
five classes, three of which include the more familiar 
kinds. These three classes are the Pelecypoda, including 
the mussels, cockles, clams, scallops, oysters, etc., mol- 
luscs with a shell composed of two pieces, one on each 
side of the body and hinged together ; the Gastropoda, 
including the snails, slugs, periwinkles, whelks, and a host 
of other univalved shell-fish, that is, molluscs which have 
a shell composed of a single piece ; and the Cephalopoda, 
including the squids, cuttlefishes, octopi, and the pearly 
nautilus. 

Clams, scallops, and oysters (Pelecypoda). — Technical 

Note. — Shells of scallops, oysters, and sea-mussels should be had for 
examination ; also specimens of Teredo or Pholas in alcohol or for- 
malin, and pieces of pile bored by Teredo. Make drawings of vari- 
ous bivalve shells, and of Teredo. 

The fresh-water mussel which we have studied is an 
example of the bivalve molluscs. The members of this 



hinge ligam 



reno pericardial aperture s 
renal aperture % 
genital aperture % 



right auricle 
anterior aorta \ 



umbone 



hinge tooths .._ 



stomach- 

digestive gtan d. 



gullet— — 
cerebro-pleural ganglion- J^ 
mouth 



anter adductor*' { 

anter retractor 
pedal ganglion 

foot 




intestine' 
typhlosole'' 



gonad 
Fig. 103.— Dissection of 



ventricle 
i 

) 

; pericardium 

j 

rectum 
' kidney 

^■dorsal pallial aperture 
posterior aorta 

post, retractor 

post adductor 
amis 

.- — "dK~-- ^fcyi visceral ganglion 

m -^^'w^B -'W -^W - exhalant sip ho n 

xf l^ $ super branchial chamber 

28? E| |J / 

$*f Mi mm<« " jT^'Mfft*" -w^a* m// 

inhalant siphon 

pallial groove 

mantle 

\ 
\ 

mantle cavity 

sh-water mussel, £W<? sp. 




MOLLUSCA: THE MOLLUSCS 247 

class show a range in size from the little fresh -water 
Cyclas about 1 cm. long to the giant clam of the Indian 
and Pacific islands ''which is sometimes 60 cm. (2 feet) 
in length and 500 pounds in weight." They show also 
some variety in the form and appearance of the shell, but 
not anything like the degree of variety shown by the 
shells of the Gastropods. 

The edible clams are of several different species. The 
hard-shell clam (Venus mercenarid) y or " quohog "as it 
is often called, is found along the Atlantic coast from 
Texas to Cape Cod. It is "common on sandy shores, 
living chiefly on the sandy and muddy plots, just beyond 
low-water mark. ... It also inhabits estuaries, where it 
most abounds. It burrows a short distance below the 
surface, but is frequently found crawling at the surface 
with the shell partly exposed. " The shells of this edible 
clam are white. The soft-shell clam [Mya arcnaria), 
4 'the clam par excellence, which figures so largely in the 
celebrated New England clam-bake, is found in all the 
northern seas of the world. . . . All along the coasts of 
the eastern States, every sandy shore, every mud flat, is 
full of them, and from every village and hamlet the clam- 
digger goes forth at low tide to dig these esculent 
bivalves. The clams live in deep burrows in the firm 
mud or sand, the shells sometimes being a foot or fifteen 
inches beneath the surface. When the flats are covered 
with water his clamship extends his long siphons up 
through the burrow to the surface of the sand, and 
through one of these tubes the water and its myriads of 
animalcules is drawn down into the shell, furnishing the 
gills with oxygen and the mouth with food, and then the 
water charged with carbonic acid and foecal refuse is 
forced out of the other siphon. When the tide ebbs the 
siphons are closed and partly withdrawn. " Ocean clams 
and mussels have furnished food for man for ages, and 



248 



ELEMENTARY ZOOLOGY 



along coasts are found here and there great mounds 
made of heaps of clam-shells which have become covered 
over with soil and vegetation. Such mounds are the old 
feasting-places of the early coast inhabitants, and the 
archaeologist often finds in these "kitchen-middens," as 




Fig. 104. — A group of marine Pacific Coast molluscs; in upper left-hand 
corner. Purpura saxicola; next to the right, Littorina scutulata] 
farthest to right, limpets, Acmara spectrum; left-hand lower corner, 
Mytilus calif ornianus; in right-hand lower corner the black shells just 
above the large clam-shell, Chlorostomum funebrale. (FYom living 
specimens in a tide pool in the Bay of Monterey, California.) 



they are called, various relics of the early natives of the 
continent. 

Even more widely known that the clams are the oysters 
{Ostrea virginianti), also members of this class of mol- 
luscs. The oyster is carefully cultivated by man in many 
countries. It has its two shells or two shell-halves dis- 
similar, one valve being hollowed out to receive the body, 
while the other is nearly flat. The oyster is attached to 
the sea-bottom by the outside of the hollowed-out valve. 
When first hatched the young oyster swims freely by 
means of its cilia; after a few days it attaches itself to 



MOLLUSCA: THE MOLLUSCS 



249 



some solid object and grows truly oyster-like. Much care 
has to be taken in cultivating oysters to furnish proper 
conditions for growth and development. The young 
oysters when first attached are called "spat"; when a 
little older this "spat," now called "seed," may be 
transplanted to new beds, which are stocked in this way. 
In fact some beds have constantly to be thus restocked, 
the young oysters produced on them not finding good 
places to attach themselves, and so swimming away. 
Sometimes pieces of slate, pottery, etc., are strew T ed about 
the oyster-beds to serve as "collectors," that is, as 
places for the attachment of the young oysters. The 




Fig. 105. — Dactylus sp., a mollusc, excavating granite. (Photograph by 
C. H. Snow; permission of Amer. Soc. Civil Engineers.) 

extent of the acreage of the American oyster-beds is 
larger than that of any other country. ' * The Baltimore 
oyster-beds on the Chesapeake River and its tributaries 
cover 3,000 acres, and produce an annual crop of 25,000,- 
000 bushels. " 

The " pearl-oyster " is not a true oyster, that is, not a 
member of the family to which the edible oysters belong, 



250 



ELEMENTARY ZOOLOGY 



but it is a member of the same class, that is, it is a bivalve 
mollusc. Pearls are obtained from a number of different 
' ' pearl-oysters, ' ' but the finest pearls and mother-of-pearl 
come from the tropical species Meleagrina mai'garitifera. 
This pearl-oyster "has an extensive distribution, being 
found in Madagascar, the Persian Gulf, Ceylon, Australia, 
Philippine Islands, South Sea Islands, Panama, West 
Indies, etc' Mother-of-pearl is simply the inner lining 
of the shell, which is composed of numerous thin layers of 
carbonate of lime so arranged that the edges of the suc- 
cessive layers produce many fine striae very close together. 
The beautiful iridescence of this inner shell-lining is 
caused by the complicated diffraction and reflection (inter- 
ference effects) of the light by the fine striae and the 
translucent superposed thin plates of shell material. 
Pearls are simply isolated deposits of shell material usually 
around some particle of foreign substance which has found 




Fig. 106. — Pholas sp., a mollusc, burrowing in sandstone. (Photograph 
by C. H. Snow; permission of Amer. Soc. Civil Engineers.) 

lodging in the mantle-cavity. Sometimes small objects 
are purposely introduced into the shell in order to stimu- 
late the formation of pearls. The pearl-fishers go out in 
boats and dive to the bottom, filling baskets with pearl- 
oysters. These are piled up in a bin and left to die and 



MOLLUSC A: THE MOLLUSCS 251 

decompose. " When the flesh is pretty thoroughly dis- 
integrated, it is washed away with water, great care being 
taken that none of the pearls loose in the flesh are lost. 
When the washing is concluded the shells themselves are 
examined for pearls which may be attached to the interior 
of the valves. ' The principal pearl-fishery is that on the 
coast of Ceylon; pearl-fishing has been carried on here 
for over 2000 years. 

The ship-worm {Teredo) is an interesting member of 
this class of bivalve molluscs, because of its unusual 




Fig. 107. — Martesia xylophaga, a Pholad, in Panama mahogany. (Photo- 
graph by C. H. Snow; permission of Amer. Soc. Civil Engineers.) 

habits, and strangely modified body form. The teredo 
is long and worm-like in general appearance, with a small 
bivalve shell at one end and two elongated siphons at the 
other. The young teredo is a free- swimming ciliated 
embryo like the young of the other bivalve molluscs, but 
it soon settles on a piece of submerged wood, usually the 
pile of a wharf, or the bottom of a ship, and burrows into 
this wood. As it grows it enlarges and deepens its tube- 
like burrow, and lines it with a calcareous deposit. The 
burrow may be a foot long or longer, and when thousands 
of teredos attack a pile or the bottom of a ship, the wood 
soon becomes riddled with holes. These boring molluscs 



2 52 ELEMENTARY ZOOLOGY 

do great damage to wharves and ships. In Holland 
where they were first discovered they caused such injuries 
to the piles and other submerged wood which supported 




Fig. 108. — The giant yellow slug of California, Ariolimax calif ornica. 
This slug reaches a length when outstretched of 12 inches. (From 
living specimen.) 

the dikes and sea-walls that they seriously threatened the 
safety of the country. 

Snails, slugs, nudibranchs and " sea-shells" (Gas- 
tropoda). — Technical Note. — Pond-snails can be readily found 
clinging to submerged stems, leaves, or pieces of wood in almost 
any pond. Collect some and carry alive, in a jar of water, to the 
schoolroom. Observe the habits of these live snails in the school aqua- 
rium. Note the movements, the coming to the surface to breathe, 
the eating (by scraping the surface of the leaves with the " radula " 
or tongue ; provide fresh bits of cabbage or lettuce-leaves)-, the use 
of the feelers. Make drawings illustrating these habits. Examine 
the shell ; note that it is univalved, that is, composed of one piece. 
Do the whorls of all the shells turn the same way ? Make a draw- 
ing of the shell, naming such parts as the apex, spire (all the whorls 
taken together), the aperture, the columella (the axis of the spire), 
the lip (outer edge of the aperture), the lines of growth (parallel to 
the tip), the suture (the spiral groove on the outside). Examine the 
snail ; note the character of the foot ; note the protrusible tentacles 
or feelers, the eyes (dark spots at bases of the tentacles), the mouth, 
the respiratory opening (on right side of body in the edge of the 
mantle which protrudes beneath the lip when the snail's body is ex- 
tended), the radula or ribbon-like tongue with fine teeth. Compare 
with the body of the mussel. 

Slugs may be found during the day concealed under boards or 
elsewhere; they are nocturnal in habit. If specimens can be ob- 
tained, compare with the pond-snails, noting the absence of a shell, 
and the fleshy mantle on the dorsal surface near the head ; note the 
presence of two pairs of tentacles (the eyes being at the tips of the 



MOLLUSC A: THE MOLLUSCS 253 

second or hinder pain, and the respiratory pore. Note the streak 
of mucus left by the slugs in crawling about. 

Some sea-shells can be got from private collections of " curios" 
to illustrate the variety of form of the univalve shells. 

Perhaps one-half of all the known species of molluscs 
are snails and slugs (fig. 108). Snails are either aquatic or 
terrestrial in habit, but in either case they (the true pulmo- 
nate snails) breathe not by means of gills, as do most of 
the other molluscs, but by means of a so-called "lung." 
This lung is a sac with an external opening on the right 
side of the body and with its inner surface richly furnished 
with fine blood-vessels. The exchange of gases between 
the blood and the outer air takes place through the thin 
walls of the blood-vessels. Most snails which live in the 
water, as the pond-snails and the river-snails, have to 
come occasionally to the surface to breathe. These fresh- 
water and land -molluscs which possess a lung-sac instead 
of gills constitute the order Pulmonata. The pulmonate 
pond- and land-snails and slugs are vegetable feeders and 
where they occur in large numbers do much injury to 
vegetation. While the common pond-snails have but 
one pair of feelers, at the base of which are found the 
eyes, most of the land-snails and slugs have two pairs of 
4 'horns," the eyes being on the tips of the second pair. 
The lung-sac, besides serving as a breathing organ, also 
enables the snail to rise or sink according as the animal 
varies the size of the sac and consequently the amount of 
air in it. All the Pulmonata are hermaphroditic, each 
individual producing both sperm- and egg-cells, The 
eggs of the pond-snail " are laid in gelatinous transparent 
capsules, half an inch to an inch in length, flattened and 
linear or oblong in outline. After a few snails have been 
kept a short time in a small vessel of water with their 
appropriate food, these egg-capsules may be looked for 
on the bottom and sides of the vessel or closelv adherent 



254 ELEMENTARY ZOOLOGY 

to the stems or leaves of plants placed in the water. 
They are so transparent as to be easily overlooked. ' : 
Young snails may be reared from these eggs. 

There are other snails common in ponds, also called, 
like the pulmonate forms, pond-snails, which have gills 
and no lung-sac. These pond-snails belong to a different 
order of molluscs, and live on the bottom of the pond, 
crawling about in the soft mud and feeding on animal 
instead of vegetable food. 

The shells of the various kinds of snails vary much. 
In many of the land-snails the spiral is. not spire-shaped 
or conical, but is flat. In some the whorls of the spiral 
run from left to right (dextral) when the shell is looked 
at with apex held toward one, while in others the whorls 
run from right to left (sinistral). 

Of the hosts of marine Gastropods we can notice only 
a few kinds. The nudibranchs (fig. 109) are a group G f 




Fig. 109. — Three Pacific Coast nudibranchs; Doris tuberculata (in lower 
left-hand corner), Echinodoris sp. (upper one), and Triopha modesta 
(at right). (From living specimens in a tide-pool on the Bay of Mon- 
terey, California.) 

beautiful forms in which the shell is wholly wanting and 
the mantle is usually absent. The gills are thus exposed 
and are usually in the shape of delicate freely projecting 



MOLLUSC A: THE MOLLUSCS 255 

tufts arranged in rows along the back. The body is often 
strikingly and variedly colored. These soft, naked " sea- 
slugs ' live near the shore, creeping about among the 
rocks and seaweeds. About a thousand species of nudi- 
branchs are known. 

Among the shell-forming marine Gastropods there is 
great variety in the size and shape and coloring of the 
shells. Many are beautifully colored and patterned; 
others are oddly and fantastically shaped. The cowries, 
or porcelain shells, familiar in collections of ocean curiosi- 
ties, have a large body whorl and a very short flat spire, 
and the brightly colored shell looks as if enamelled. 
Some of the coast tribes of Africa once used, and perhaps 
still use to some extent, cowries as money. The limpets 
(fig. 104) are among the most abundant of the seashore 
molluscs, their low, broadly conical shells being plenti- 
fully scattered over the rocks between tide-lines. The 
' ' oyster-drills ' ' are Gastropods with odd spiny shells which 
do much harm in oyster-beds by settling down on the 
oysters, boring holes through the shells and eating the 
soft parts within. The helmet-shells, from which shell 
cameos are cut, are composed of layers of shell material 
of different colors. Among the specially beautiful shells 
are the cone-shells, the olive-shells, the ivory-shells, etc. 

Squids, cuttlefishes, and octopi (Cephalopoda). — 

Technical Note. — Small squids preserved in alcohol or formalin 
can be had of all dealers in biological supplies (see p. 453;, and 
specimens should be examined. 

The squids (fig. no), cuttlefishes, octopi or "devil- 
fishes," and the three living species of Nautilus constitut- 
ing the class Cephalopoda are very different from the other 
molluscs in appearance, and are in fact different in im- 
portant structural characters. They can move swiftly, 
have strangely modified organs of prehension, strong biting 
mouth-parts, and eyes of very complex organization. 



2 5 6 ELEMENTARY ZOOLOGY 

They are the most highly organized molluscan forms, and 
their predaceous habits and the great size to which some 
of them attain have given them distinction among the 
fierce and dangerous creatures of the sea. They are all 
strictly marine in habitat, and are all carnivorous. Most 
of them have no shell, or where the shell is present it is 
internal in all but a very few forms. The tentacle-like 
arms or feet surrounding the mouth which occur in all the 
Cephalopods are provided with sucking organs or suckers, 
in some cases w 7 ith a horny toothed rim. These long, 
powerful, grasping, tentacular feet, with the suckers and 
five hooks, are very effective means of securing prey, and 
the pair of strong, sharp, cutting mandibles or beaks are 
equally effective in tearing to pieces. The eyes of the 
Cephalopods are almost as highly developed as those of 
the vertebrates. They are unusually large and staring, 
and add much to the terrifying appearance of the " devil- 
fishes.' : Cephalopods have the power of quickly chang- 
ing color, because of the presence in the skin of many 
pigment-cells which can expand so as nearly to touch 
each other, thus producing a uniform tint over the whole 
body, or which can contract so as to destroy this uniformity 
of color. There are several sets of these color-carrying 
cells or chromatophores, each set of a color different from 
the others. The purpose of this change of color is pro- 
tective, the animal being thereby able to make its color 
so harmonize with that of its immediate surroundings as 
to become indistinguishable. 

There are two principal groups of Cephalopods, viz., 
the Decapods and the Octopods. The Decapods, as their 
name indicates, have ten feet or arms surrounding the 
mouth, and in them the body is usually elongate, con- 
taining a horny "pen' or calcareous "bone.' This 
group includes the cuttlefishes or sepias, from which are 
obtained sepia ink and the cuttlefish bone used to feed 



MOLLUSCA: THE MOLLUSCS 



'57 



canary birds. The ink is a secretion which the cuttlefish 
discharges when attacked to create a cloud in the water 
and thus escape unperceived. The squids {Loligd) com- 
monly used as bait by fishermen belong to the Decapoda. 
The two extra feet or arms which the Decapods have in 
addition to the eight possessed by the Octopods, differ 
from the others in being longer and slenderer and having 
suckers only on the distal extremities which are expanded 
into " clubs " (fig. no). 

The Octopods have a short, sac-like, sub* spherical body 
and neither external nor internal shell. To this group 




Fig. iio. — The giant squid, Omrnatostrepkes califoi'jiica. (From specimen 
with body (exclusive of tentacles) four feet long, thrown by waves on 
shore of the Bay of Monterey, California.) 

belong the famous devil-fishes {Octopus), whose strange 
and terrifying appearance combined with their frequently 
great size has furnished the basis for many a weird tale of 
the sea. Octopi have been killed having tentacles more 
than 30 feet in length. The largest members of the 
class, however, are probably the giant squids (belonging 
to the Decapoda) specimens of which have been captured 
with a body-length of twenty feet, and arms thirty-five 
feet long. 

The beautiful paper sailor or argonaut {Argonauta argoY 



258 ELEMENTARY ZOOLOGY 

which secretes a thin shell (not homologous with the 
shell of the other molluscs) to protect her eggs, is a mem- 
ber of the Octopod group. In fine weather the argonauts 
sail in fleets on the surface of the ocean. 

The pearly nautilus (Nautilus pompilius) is a Cephalo- 
pod with four gills instead of two, as with the Decapoda 
and Octopoda, and is the only existing member of what 
was in the earlier times of the earth's history a large 
group of animals. The nautili live in rather shallow 
water usually creeping over the bottom feeding on small 
marine animals. They make a many-chambered spiral 
shell with its inner surface lined with beautiful pearly 
nacre. 



CHAPTER XXIII 

BRANCH CHORDATA: THE VERTEBRATES, 
ASCIDIANS, ETC. 

The branch Chordata includes all the backboned 
animals or vertebrates, comprising the fishes, salamanders, 
frogs and toads, lizards, crocodiles, turtles and snakes, 
birds, and all the quadrupeds or mammals, and includes 
also a few small unfamiliar ocean animals which do not 
look at all like the backboned animals, but which agree 
with them in possessing a peculiar structure called the 
notochord. This notochord consists of a series or cord of 
cells extending longitudinally through the body from head 
to tail, above the alimentary canal and below the spinal 
nerve-cord. In all the vertebrates excepting a few low 
forms, the notochord while present in the young, is re- 
placed in the adult by a segmented bony or cartilaginous 
axis, the spinal or vertebral column. But in the ascidians 
or sea-squirts (called also tunicates) it persists throughout 
life. In addition to this characteristic notochord, nearly 
all the Chordata are marked by the presence, either in 
embryonic or larval stages only, or else persisting through- 
out life, of a number of slits or clefts in the walls of the 
pharynx which serve for breathing, and which are called 
gill-slits. 

Structure of the vertebrates. — As the backboned or 
vertebrate animals make up almost the whole of the 
branch Chordata, and as the few other chordates are 
animals the special structures of which we shall not under- 
take to study in this book, we may note here some of the 
other more obvious structural characteristics of the true 

259 



260 ELEMENTARY ZOOLOGY 

vertebrates. The possession of a backbone or bony 
(sometimes cartilaginous) spinal column is the character- 
istic by which we distinguish them from the invertebrate 
or backboneless animals. Furthermore, all of the verte- 
brates possess an internal skeleton which is in most cases 
composed of bone, and is firm and strong. In some of the 
lower fishes, as the sharks and sturgeons, the skeleton is 
made up of cartilage, tough but not hard. The vertebrate 
skeleton consists typically of an axial portion comprising 
the spinal column and head, and of two pairs of append- 
ages or limbs, variously developed as fins, wings, legs 
and arms. In some vertebrates these limbs are repre- 
sented by mere rudiments, and in the lowest fish-like 
forms, the lancelets and lampreys, there is not the 
slightest trace of limbs. A part of the central nervous 
system^ the spinal cord, runs longitudinally through the 
body on the dorsal side of the alimentary canal; the cir- 
culatory system is closed, the blood being always confined 
in the heart and in vessels called arteries, veins, and capil- 
laries, and the blood is red in color owing to the presence 
of numerous red corpuscles or blood-cells. The nervous 
system is highly developed, with a large brain in all the 
typical forms, and with complex and usually highly 
efficient special sense-organs. Respiration is carried on 
by means of external gills, or by internal lungs which 
communicate with the outside through the mouth and 
nostrils. To the lungs and gills the blood is brought to 
be " purified," i.e., to give up its carbonic-acid gas and 
to take up oxygen. 

Classification. — The Chordata are variously divided 
by zoologists into eight or ten classes, of which (in the 
eight-class system) the five classes * Pisces (fishes), 

* The animals included by some zoologists in the single class Pisces, are 
held by other zoologists to constitute three distinct classes, thus making a 
subdivision of the branch into ten classes. 



BRANCH CHORD AT A: THE VERTEBRATES, ETC. 261 

Batrachia (batrachians), Reptilia (reptiles), Aves (birds), 
and Mammalia (mammals), belong to the true vertebrates. 
These classes will be considered in the five following 
chapters. 

The remaining three classes include a number of strange 
marine forms which until recent years were considered as 
worms, but which are now known to be the nearest living 
allies of the earliest or primitive vertebrates. The rela- 
tionship of these forms to early types is manifest, not in 
the appearance or structure of the adult stage, but only 
during embryonic or larval stages. 

The ascidians. — The sea-squirts, or Ascidians, com- 
mon on the seashore, compose one class of these primitive 







Fig. hi. — An ascidian or sea-squirt from the coast of California. (After 

Jordan and Kellogg.) 

chordate animals. They possess a simple, sac-like body 
(fig. 111), fastened to the rocks by one end, the other being 



262 ELEMENTARY ZOOLOGY 

provided with two openings, one for the ingress and the 
other for the exit of water, a strong current of which flows 
constantly through the body. By means of this current 
the ascidian obtains food. Usually sea-squirts live 
together in large colonies, and in some cases a number of 
individuals enclose themselves in a common gelatinous 
mass, forming what is called a compound ascidian. 

The ascidian when born is a tiny, free-swimming, tad- 
pole-like creature with a slender finned tail. It swims 
about freely for only a few hours, however, soon attach- 
ing itself to a rock, and in its further development becom- 
ing degenerate. It loses its tail and with it the short 
notochord possessed by the larva ; the eye and the auditory 
organ are lost, and the nervous system and alimentary 
canal become much reduced and simplified. Sea-squirts 
in their adult stage are very simple degenerate animals, 
with low functional development, yet their embryonic and 
larval conditions show a considerable degree of structural 
specialization, and the presence of the notochord in these 
early stages reveals their affinity with the backboned 
animals. 



CHAPTER XXIV 

BRANCH CHORDATA {Continued)' CLASS PISCES 

(THE FISHES) 

THE GOLDEN SUNFISH OR PUMPKIN SEED (Apomotis sp.) 

Technical Note. — The species of sunfish named, or some closely 
related species, can be obtained in any brook or stream in the 
United States. Gibbosus lives in all streams north of Dubuque, 
Chicago, Pittsburg, and along the eastern coast north of Charleston. 
Closely allied species live in all the other parts of the countn 
except in the higher Rocky Mountains west of Bismarck, Pueblo, 
and Santa Fe. One species is found in the streams of California, 
but none occurs in Washington or Oregon. In the few places 
where a sunfish cannot be had, any species of bass or perch may 
be used. Sunfish live in ponds and sluggish streams in deep holes 
under a log or at the foot of a stump. They take eagerly a hook 
baited with a worm, or they may be caught in nets. When sun- 
fish cannot be kept fresh for study in class, specimens may be 
preserved in alcohol or \% formalin. But if possible to keep some 
alive for a time in a jar or tub with plenty of fresh water, the colors 
of the living fish, together with its manner of swimming and mode 
of breathing, can be observed. 

External structure * (fig. 1 12). — Examine the general 
configuration and make-up of the body. Note the deep, 
laterally flattened trunk and paddle-like tail. The head 
is closely fitted to the trunk without any neck. Note that 

* The author wishes to call the attention of teacher and student to the 
plan (referred to in the Preface, page v) adopted in writing the directions 
for the dissections. The sequence of the references to the various organs 
depends on the actual course of the dissection, and not upon the association 
of organs in systems. And the directions are so much condensed that they 
are hardly more than a means of orienting the student, leaving him to work 
out independently, or by the aid of more detailed accounts (sometimes 
specifically referred to), the details of the dissection. 

263 



264 ELEMENTARY ZOOLOGY 

the body is thickly covered with firm, hard scales , arranged 
like the shingles on a roof. Remove one of these scales 
and examine it under a hand lens. What sort of an edge 
has it ? Such a scale is said to be ctenoid. 

The body of the sunfish terminates behind in the 
caudal fin, a series of cartilaginous rays connected by thin 
skin and attached to a bony plate at the end of the back- 
bone. Along the median dorsal line will be noted another 
fin composed anteriorly of spines and posteriorly of soft 
rays jointed and branched. This is the dorsal fin. How 
many spines has it ? Anterior to the caudal fin on the 
ventral surface is a median unpaired anal fin. How many 
spines has it ? Anterior to the anal fin are the ventral 
fins, while on the sides of the body back of the head in 
a line with the mouth are found the pectoral fins. The 
ventral fins, attached to a rudimentary pelvis, correspond 
to the hind legs of the other vertebrates. The pectoral 
fins, attached to the shoulder girdle, correspond to the 
arms. In front of the anal fin note a small pit-like open- 
ing, the opening from the kidneys and reproductive organs, 
and just anterior to this a large aperture, the amis. At the 
anterior end of the head note the broad mouth, surrounded 
by a complicated system of bones. Note the large eyes 
surrounded by a series of small bones, the orbital chain. 
Just anterior to the eyes are two pairs of openings, one 
pair of each side opening into a closed sac. What are 
these openings ? Note the presence of various bones on 
the side of the head, each covered with a thin layer of 
skin. These are membrane bones, characteristic of fishes. 
Are there any external ears in the fish ? Examine the in- 
side of the mouth. Is there a tongue f If so, of what char- 
acter ? Are there teeth ? If so, where are they situated ? 

Note along each side extending to the base of the tail 
a line of modified scales, on each scale a little mucous 
tube, the whole series constituting the lateral line. These 



BRANCH CHORD AT A; CLASS PISCES: THE FISHES 265 

scales are intimately associated with a large nerve (the 
vagus), and probably serve an important part, not yet 
clearly understood, in the life of the fish. 

Lift up the flap in front of one of the pectoral fins. 
This is the opercular flap which covers the gills that lie 
beneath. Bend this forward and find four gill-arches, 
each with its double fringe of gills. Note the gill-rakers , 
short and blunt, on the first gill-arch. Note also on the 
under side of the flaps turned back, delicate red gill-like 
structures covered by a membrane. These are the false 
gills or pseudo-branchiae, larger in most fishes than in the 
sunfish. The gills in the fish subserve the same function 
as the gills of the crayfish, that of purifying the blood 
by eliminating carbonic-acid gas from it and taking up 
oxygen from the air mixed with or dissolved in the water. 
Organs subserving the same purposes in different kinds of 
animals as, for example, the gills in fish and in crayfish, 
are called analogous structures. But there is an important 
morphological difference between the fish's gills and the 
gills of the crayfish. In the latter animal they are out- 
growths of the basal segments of the walking-legs ; in the 
fish they are outgrowths from the alimentary Ganal. The 
internal gills of the young toad (tadpole) arise in the same 
way as those of a fish. Structures which are identical in 
their origin, like the gills of tadpole and fish, are called 
homologous structures. 

Make a drawing of the sunfish from a lateral aspect, 
showing the external parts named. 

Internal Structure. — Technical Note.— Insert one point 
of the scissors a little to one side of the anus and cut dorsally on the 
left side of the body to the backbone. Now cut anteriorly from the 
anus along the ventral wall to where the jaws unite, and cut, also 
anteriorly, along the dorsal wall until the left side of the body can 
be removed. Bend the opercular flap backward over the eye and 
pin the entire fish, uncut side down, to the bottom of the dissecting- 
pan, covering it with water. 



266 ELEMENTARY ZOOLOGY 

The above operation will have severed the large power- 
ful muscles forming the body-wall and extending along 
the sides. Note a membranous sac completely filling a 
large dorsal cavity. This is the swim-bladder, a float 
filled with air which tends to give the fish the same weight 
as the water it displaces. It arises as a diverticulum from 
the alimentary canal, but soon becomes permanently shut 
off from it. Beneath the swim-bladder is a large cavity 
filled with various organs, collectively known as the 
viscera. In vertebrate animals the cavity which contains 
the viscera is generally called the peritoneal cavity. It is 
lined by the peritoneum, a delicate membrane, part of 
which is deflected as the mesentery over the alimentary 
canal and the other organs, thus suspending them all from 
the dorsal wall. Note in the anterior end of the peritoneal 
cavity a large bi-lobed gland, the liver, red in fresh, 
yellowish in alcoholic specimens. Its function, like that 
of the liver of the toad, is to store up nutriment for the 
blood and to secrete a digestive fluid called bile. Behind 
the liver note a long, convoluted tube. What is this tube ? 
Unfold this tube, separating it from its enveloping mem- 
brane, the mesentery. Thrust a probe down the throat 
and note that it passes into a thick-walled sac, the 
stomach. The mouth and gill-slits open into the front 
part of the alimentary canal called the pharynx, which 
leads by a short tube, the oesopliagus, into the stomach. 
Note the large, thickened portion of the alimentary canal 
leading from the stomach. This is the pyloi'its, and to its 
walls are attached a number of finger-like projections, the 
pyloric cceca. The pyloric caeca secrete a fluid which is 
poured into the alimentary canal and which assists in the 
process of digestion somewhat as does the secretion from 
the pancreas of the toad. From the pylorus, passing 
backwards in one or two loops, is the small intestine. 
Trace this to its exit. Lying within the mesentery near 



BRANCH CHORD AT A; CLASS PISCES: THE FISHES 267 

the posterior end of the body-cavity note a small red 
glandular mass, the spleen. 

At the anterior end of the body in front of the liver 
and between the sets of gills note the small pericardial 
cavity within which is contained the heart. The peri- 
cardial cavity is separated from the peritoneal cavity by 
a thick muscular wall against which the liver abuts. The 
heart consists of four parts. The posterior part is a thin- 
walled reservoir, the sinus venosus, into which blood 
enters through the jugular vein from the head and through 
the cardinal vein from the kidney. From the sinus 
venosus it passes forward into a large chamber, the 
auricle. Next it flows into the ventricle, where, by the 
contraction of the walls, rhythmical pulsations force it into 
the conns arteriosus, thence into the ventral aorta, and 
lastly into the gills, where it is purified. After passing 
through the capillaries in the fine gill-filaments it is again 
collected, now pure, by paired arteries from each pair of 
gills, which arteries unite to form the dorsal aorta ex- 
tending backward just below the backbone to the end of 
the tail. From the dorsal aorta a pair of arteries, the 
subclavian, are given off to the pectoral fins. At this 
point tw r o other arteries branch off ventrally, the first being 
the cardiac artery, which distributes blood to the stomach 
and pyloric caeca. The second divides into several long 
mesenteric arteries supplying blood to all parts of the in- 
testine and spleen. In the caudal region blood is taken 
up through the caudal vein and carried forward to the 
kidneys. These strain out the impurities arising from 
waste of tissues, after which the blood is carried back to 
the sinus venosus through the cardinal vein. From the 
intestine it is gathered into the large portal vein as in the 
toad. The portal vein carries blood to the liver, where 
nutriment may be stored up, and from thence it flows back 



268 ELEMENTARY ZOOLOGY 

to the sinus venosus through a very short thin-walled 
vessel, the hepatic sinus. 

The kidneys, more or less united in one mass, lie in the 
posterior part of the body-cavity along the dorsal wall. 
Note running from each side of the kidney a ureter which 
unites with its fellow and opens into a small urinary 
bladder which discharges through a small opening im- 
mediately back of the anus. 

The reproductive organs lie below the swim-bladder 
near the posterior end of the body-cavity. If the fish are 
caught in the spring, the greater part of the body-cavity 
of the female is found to be filled with small eggs. When 
mature, these eggs are deposited by the mother fish in the 
gravel of the stream-bed where they are fertilized by the 
sperm-cells poured over them by the male and left float- 
ing in the water. 

The nervous system of fishes is best studied in a speci- 
men treated with nitric acid. Carefully remove the roof 
of the skull, thereby exposing the brain. Most anteriorly 
make out, as in the toad, the paired olfactory lobes. 
These are attached by long stalks to the cerebrum or 
forebrain, which is followed by two large hollow lobes, 
the midbrain or optic lobes. Behind the midbrain is the 
cerebellum. Following the cerebellum is the elongate 
medulla oblongata, which tapers backward into the spinal 
cord. How far backward does the spinal cord extend ? 
On each side of the brain-case about opposite the cerebel- 
lum are located the auditory organs, each consisting of 
three semicircular canals which lie in different planes, and 
of the vestibule. These parts are filled with liquid, and 
suspended in the liquid in the vestibule are small calcareous 
bodies called otoliths or ear-stones. Running out beneath 
from the midbrain are the optic nerves, which cross, the 
left one connected with the right eye, the right one with 
the left eye. From each side of the medulla oblongata 



BRANCH CHORD AT A; CLASS PISCES: THE FISHES 269 

there is given off a large nerve, the vagus, which, sends 
branches to the lateral line organs on either side, and 
extends backward to the stomach and viscera. 

For further study of the nervous system see Parker's 
44 Zootomy/' pp. 1 22-130. 

Make a drawing of the nervous system as worked out. 

Technical Note. — To make a good skeleton immerse a fresh 
or preserved specimen for some time in a hot soap solution. When 
the muscles have commenced to soften remove the body from the 
solution, pick the flesh away, and leave to dry. 

Note that the main axis of the skeleton is composed of 
vertebra placed end to end. How many vertebrae are 
there ? What vertebrae bear ribs ? The ribless ones 
beyond the body-cavity are called caudal vertebrce. Note 
the interspinal bones which support the fins, with large 
muscles on either side to control their action. Note that 
the group of bones supporting the pectoral fin is attached 
to the back of the brain-case and makes up the shoulder 
girdle. The ventral fins are attached to a rudimentary 
pelvic girdle, attached in front to the shoulder girdle, as 
the shoulder girdle is in turn attached to the skull. It 
will be seen that the sunfish has no neck and we may say, 
also, no back. Its skeleton consists only of a tail attached 
to the skull. The brain-case is made up of a number of 
bones closely joined together. From it is suspended the 
lower jaw, which comprises a number of bones but loosely 
attached to each other. Overlying these is the system 
of membrane bones already mentioned, including the 
opercle or gill-cover. 

For a detailed study of the fish-skeleton see Parker's 
"Zootomy," pp. 86-101, or Parker and Haswell's 
"Zoology," vol. II. pp. 183-195. 

Life-history and habits. — The sunfish or "pumpkin- 
seed ' lives in quiet corners of the brooks and rivers, 
preferably under a log or at the root of an old stump. It 



270 ELEMENTARY ZOOLOGY 

is a beautiful fish, shining "like a coin fresh from the 
mint." Its body is mottled golden, orange and blue, 
with metallic lustre, darker above, pale or yellowish 
below. Its fins are of the same color. The tip of its 
opercle is prolonged like an ear and jet black in color, 
with a dash of bright scarlet along its lower edge. Nearly 
all the thirty species of sunfish found in the United States 
have this black ear, but some have it long, some short, 
and in some it is trimmed with yellow or blue instead of 
scarlet. 

The sunfish lays its eggs in the spring in a rude nest it 
scoops in the gravel, over which it stands guard with its 
bright fins spread, looking as big and dangerous as 
possible. When thus employed it takes the hook savagely, 
perhaps regarding the worm as a dangerous enemy. The 
young fishes soon hatch, looking very much like their 
parents, although more transparent and not so brightly 
colored. They grow rapidly, feeding on insects and 
other small creatures, and reach their growth in two or 
three years. They do not wander far and never willingly 
migrate. Students should verify this account on the 
different species. A more exact study of the nests of the 
different species and the fishes' defence of them would be 
a valuable addition to our knowledge. The most striking 
traits of the habits of this fish are its vivacity and courage ; 
it reveals its great muscular strength when captured. 
The sexes are similar in appearance and both defend the 
nest alike. 

OTHER FISHES. 

Fishes constitute the largest class of vertebrate animals 
and are to be found everywhere in ponds, streams, or 
ocean. About 15,000 species offish are known, of which 
3,000 live in North America. The largest of all fishes is 
the basking shark (Cetorhinus), which reaches a length 



swim-bladdi 



lateral line 



opercular flap 

stomach 



gill-rakers 



gall bladder 



nostrils 




tongue 



s pyloric cae 



ventricle 
conus arteriosus 



ventral fin ^% \ *"&*** 
body cavity 



Fig. 112. — Dissectio 



f cavity of the swim-bladder 
s' kidney 




anus 



urinary bladder 
opening from kidneys 



body muscles 



e sunfish, Apomotis sp. 



BRANCH CHORD AT A ; CLASS PISCES: THE FISHES 271 

of thirty-six feet. The smallest is the dwarf goby 
(Mistickthys), less than half an inch long, found in Luzon, 
one of the Philippine Islands. Between these extremes 
is every variety in size, form, and relative proportions. 
The body, for example, may be greatly elongated and 
almost cylindrical as in the eels; or long and flattened 
from side to side as in the ribbon-fishes ; or the head may 
be very large, wider and higher than the rest of the body 
as in the anglers, or may have a great beak as in the 
sword-fish. 

Body form and structure.— When we consider the fish 
as a whole, we find first a body formed for progression in 
the water, the typical fish being pointed at each end (the 
shorter point in front), and having the sides flattened, the 
back and belly rather narrow, and the motive power 
located in the fin on the tail. From this typical form 
diverge all conceivable variations, adaptations to every 
sort offish life. 

Most fishes have the body covered with scales, although 
many have the skin naked or covered with small scales 
so hidden in the skin as to be hardly visible. The scales 
are small horny or bony plates which fit into small pockets 
or folds of the skin, and are usually arranged shingle- 
fashion, overlapping each other. They are of various 
shapes, mostly classified as of three kinds, namely, squarish 
enamelled scales called ganoid, roundish smooth-edged 
called cycloid, and roundish tooth-edged called ctenoid. 

The skeleton of the fish is relatively complex. Its 
bones are comparatively soft, having little lime in thern, 
indeed in many cases they are mere cartilage. The 
vertebral column is made of twenty-four vertebrae in the 
typical fishes, the number in the others being variously 
increased, or sometimes diminished. These vertebrae are 
of two classes, abdominal or body, and caudal or tail 
vertebrae. The former have a neural arch which enclcse3 



2 7 2 ELEMENTARY ZOOLOGY 

the spinal cord and from which projects a spine. Below, 
the processes spread apart, surrounding the kidneys and 
partly enclosing the air-bladder. To these processes ribs 
are loosely attached. The caudal vertebrae have no ribs 
and leave no room below for viscera. Their lower arch 
(haemal), similar to the dorsal (neural) arch, surrounds a 
blood-vessel. The fins of a fish are composed of bony 
rods or rays joined by membrane. Some of these rays 
may be unbranched and unjointed, being then known as 
spines, and usually occupy the front part of the fin. 
Other rays are made up of little joints and are usually 
branched toward their tip. Such ones are called soft 
rays. Soft rays make up the greatest part of most fins. 
The vertical fins are on the middle line of the body. 
These are the dorsal above, anal below, and caudal form- 
ing the end of the tail. The paired pectoral and ventral 
fins are ranged one on each side corresponding to the 
arms and legs of higher animals. The pectoral fin or 
arm is fastened to a series of bones called the shoulder 
girdle. These bones do not correspond to those in the 
shoulder girdle of the higher animals, and the various 
parts in the two structures are differently named. The 
uppermost bone of the shoulder girdle is usually attached 
to the skull. To the lowermost is attached the rudimen- 
tary pelvis, which supports the hinder limb or ventral fin. 
Usually the pelvis is farther back and loose in the flesh, 
but sometimes it is placed far forward, being occasionally 
attached at the chin. 

The head contains the various bones of the cranium, 
usually closely wedged together and not easily distin- 
guished. The jaws are each made of several pieces ; the 
lower one is suspended from the skull by a chain of three 
flat bones. The jaws may bear any one of a great variety 
of forms of teeth or no teeth at all, and any of the bones 
of the mouth-cavity and throat may have teeth as well. 



BRANCH CHORD AT A; CLASS PISCES: THE FISHES 273 

On the outside of the head are numerous bones called 
membrane bones, because they are made up of ossified 
membrane. The most important of these is the opercle 
or gill-cover. Within are the tongue with the five gill- 
arches attached to it below and to the floor of the skull 
above, the last arch being usually modified to form the 
pharyngeal jaw. 

The stomach may be a blind sac with entrance and exit 
close together, or it may have the form of a tube or 
siphon. At its end are often found the large glandular 
tubes called pyloric caeca which secrete a digestive fluid ; 
and to its right side is attached the red spleen. The liver 
is large, having usually, but not always, a gall-bladder; 
it pours its secretion into the upper intestine. In fishes 
which feed on plants the intestine is long, but it is short 
in those which eat flesh, because flesh is digested in the 
stomach, not in the intestines. The kidney is usually a 
long slender forked glaud showing little variation. The 
egg-glands differ greatly in different sorts of fishes, the size 
and number of eggs varying equally. The air-bladder is 
a lung which has lost both lung structure and respiratory 
function, being simply a sac filled with gas secreted from 
the blood, and lying in the upper part of the abdominal 
cavity. It is subject to many variations. In the gar 
pike, bow-fin and the lung-fishes of the tropics, the air- 
bladder is a true lung used for breathing and connected 
by a sort of glottis with the oesophagus. In others it is 
rudimentary or even wholly wanting, while in still others 
its function as an air-sac is especially pronounced, and in 
many it is joined through the modified bones of the neck 
to the organ of hearing. 

The blood of the fish is purified by circulation through 
its gills. These are a series of slender filaments attached 
to bony arches. Among them the blood flows in and out, 
coming in contact with the water which the fish takes in 



274 ELEMENTARY ZOOLOGY 

through its mouth and which passes across the gills to be 
expelled through the gill-openings. The blood is received 
from the body into the first chamber of the heart, a mus- 
cular sac called the auricle. From here it passes into the 
ventricle, a chamber with thicker walls, the contraction 
of which sends it to the gills, thence without return to the 
heart it passes over the body. The circulation of blood 
in fishes is slow, and the blood, which receives relatively 
little oxygen, is cold, being but little warmer than the 
water in which the individual fish lives. 

Inside the cranium or brain-case is the brain, small and 
composed of ganglia which are smooth at the surface and 
contain little gray matter. At the posterior end of the 
brain is the thickened end of the spinal cord, called the 
medulla oblongata. Next overlapping this is the cere- 
bellum, always single. Before this lie the largest pair of 
ganglia, the optic lobes or midbrain, round, smooth, and 
hollow. From the under side of these, nerves run to the 
eyes with or without a chiasma or crossing. In front of 
the optic lobes and smaller than them is the cerebrum or 
forebrain, usually of two ganglia but sometimes (in the 
sharks) united into one. In front of these are the small 
olfactory lobes which send nerves to the nostrils. 

The sense organs are well developed. The sense of 
touch has in some fishes special organs for its better 
effectiveness. For instance certain fin-rays in some 
fishes, or, as in the catfish, slender, fleshy, whip-like 
processes on the head, are developed as feelers or special 
tactile organs. Other fishes, the sucker and loach for 
example, have specially sensitive lips and noses with 
w r hich they explore their surroundings. The sense of 
taste does not seem to be well developed in this group. 
Taste-papillae are often present in small numbers on the 
tongue or on the palate. The sense of smell is good. 
The olfactory organs, one on each side of the head, are 



BRANCH CHORD AT A; CLASS PISCES: THE FISHES 275 

hollow sac-like depressions, closed at the rear. In moc^ 
cases each sac has two openings or nostrils. The sense 
of hearing is not very keen. The ears are fluid-filled sacs 
buried in the skull, and without external or (except in a 
few cases) internal opening. Fishes are far more sensi- 
tive to sudden jars or sudden movements than to any 
sound. They possess what is generally believed to be a 
special sense organ not found in other animals. This is 
the lateral line which extends along the sides of the body 
and which consists of a series of modified scales (each one 
with a mucous channel) richly supplied with nerves. The 
eyes are usually large and conspicuous. They differ 
mainly from the eyes of other vertebrates in their myopic 
spherical crystalline lens, made necessary by the density 
of the medium in which fishes live. There are usually no 
eyelids, the skin of the body being continuous but trans- 
parent over the eyes. Being near-sighted, fishes do not 
discriminate readily among forms, their special senses 
fitting them in general to distinguish motions of their 
enemies or prey rather than to ascertain exactly the 
nature of particular things. 

The colors of fishes are in general appearance protec- 
tive. Thus most individuals are white on the belly, 
mimicking the color of the sky to the enemy which 
pursues them from below. Seen from above most of them 
are greenish, like the water, or brownish gray and 
mottled, like the bottom. Those that live on sand are 
sand-colored, those on lava black, and those among rose- 
red sea-weeds bright red. In many cases, especially 
among kinds that are protected by their activity, brilliant 
colors and showy markings are developed. This is 
especially true among fishes of the coral reefs, though 
species scarcely less brilliant are found among the darters 
of our American brooks. 

Among fresh-water fishes bright colors, crimson, 



276 ELEMENTARY ZOOLOGY 

scarlet, blue, Creamy white, are developed in the breeding 
season, the then vigorous males being the most highly 
colored. Many of the feeble minnows even become very 
brilliant in the nuptial season of May and June. Color in 
fishes is formed by minute oil-sacs on the scales, and it 
often changes quickly with changes in the nervous condi- 
tion of the individuals. 

Development and life-history. — The breeding habits 
of fishes are extremely varied. Most fishes do not pair, 
but in some cases pairing takes place as among higher 
animals. Ordinarily fishes lay their eggs on the bottom in 
shallow water, either in brooks, lakes, or in the sea. The 
eggs of fishes are commonly called spawn, and egg-laying 
is referred to as spawning. The spawn of some fishes is 
esteemed a special food delicacy. Spring is the usual time 
of spawning, though some fishes spawn in summer and 
some even in winter; generally they move from their usual 
haunts for the purpose. The eggs of the different species 
vary much in size, ranging from an inch and a half in 
diameter (barn-door skate) down to the tiniest dots, like 
those of the herring. The number of eggs laid also varies 
greatly. The trout lays from 500 to 1,000, the salmon 
about 10,000, the herring 30,000 to 40,000, and some 
species of river fish 500,000, while certain flounders, 
sturgeons, and others each lay several millions of eggs. 
The adults rarely pay any attention to the eggs, which are 
hatched directly by the heat of the sun or by heat absorbed 
from the water. The length of incubation varies much. 
When the young fish leaves the egg-shell it carries, in the 
case of most species, a part of the yolk still hanging to 
its body. Its eyes are very large, and its fins are repre- 
sented by thin strips of membrane. It usually undergoes 
no great changes in development from the first, resembling 
the adult except in size. But some of the ocean fishes 



BRANCH CHORD AT A; CLASS PISCES: THE FISHES 277 

show a metamorphosis almost as striking as that of insects 
or toads or frogs. 

Some fishes build nests. Sticklebacks build elaborate 
nests in the brooks and defend them with spirit. Sun- 
fishes do the same, but the nests are clumsier and not 
so well cared for. 

The salmon is the type of fishes which run up from the 
sea to lay their eggs in fresh water. The king salmon of 
the Columbia River, for example, leaves the sea in the 
high waters of March and ascends without feeding for over 
a thousand miles, depositing its spawn in some small 
brook in the fall. After making this long journey to lay 
the eggs, the salmon become much exhausted, battered 
and worn, and are often attacked by parasitic fungi. They 
soon die, probably none of them ever surviving to lay eggs 
a second time. 

Classification. — A fish is an aquatic vertebrate, fitted 
to breathe the air contained in water, and never develop- 
ing fingers and toes. Accepting this broad general 
definition we find at once that there are very great differ- 
ences among fishes. Some differ more from others than 
the ordinary forms differ from rabbits or birds. So 
although we have entitled this chapter as if all fishes 
belonged to the class Pisces, we cannot arrange them 
satisfactorily in less than three classes. 

The lancelets (Leptocardii). — The lowest class offish- 
like animals is that of the lancelets, the Leptocardii. 
These little creatures, translucent, buried in the sand, of 
the size and form of a small toothpick, are fishes reduced 
to their lowest terms. They have the form, life, and ways 
of a fish, but no differentiated skull, brain, heart, or eyes. 
Moreover they have no limbs, no jaws, no teeth, no 
scales. The few parts they do have are arranged as in a 
fish, and they show something in common with the fish 



278 



ELEMENTARY ZOOLOGY 



embryo. Lacking a distinct head, the lancelets are put 
by some zoologists in a group called the Acrania, as 
opposed to the Craniata, which includes all the other 
vertebrates. Lancelets have been found in the North 
Atlantic and Mediterranean, on the west coast of North 
America, on the east coast of South America and on the 
coasts of Japan, Australia, New Zealand, the East Indies 
and Malayan Islands. The best-known members of the 
group belong to the genus Ampliioxus. There are but 
one to two other genera in the class. 

The lampreys and hag-fishes (Cyclostomata). — The 
next class offish-like animals is that of the lampreys (fig. 




Fig. 113. — A lamprey, Petro7iivzon marinus. (After Goode.) 

113) and hag-fishes, the Cyclostomata. The lampreys 
and hags are easily distinguished from the true fishes by 
their sucking mouth without jaws, their single median 
nostril, their eel-like shape and lack of lateral appendages 
or paired fins. The hag-fishes {Myxine), which are 
marine, attach themselves by means of a sucker-like mouth 
to living fishes (the cod particularly), gradually scraping 
and eating their way into the abdominal cavity of the fish. 
These hags or " borers ' ' "approach most nearly to the 
condition of an internal parasite of any vertebrate.' The 
lampreys, or lamprey-eels as they are often called because 
of their superficial resemblance to true eels, are both 
marine and fresh-water in their habitat, and most of them 
attach themselves to live fishes and suck their blood. 
They also feed on Crustacea, insects, and worms. The 



BRANCH CHORD AT A; CLASS PISCES: THE FISHES 27$ 

brook-lamprey, Lampetra wilderi, is never parasitic. It 
reaches its full size in larval life and transforms simply 
for spawning. The sea- and lake-lampreys ascend small 
fresh-water streams when ready to lay their eggs, few 
living to return. Sometimes small piles of stones are 
made for nests. The young undergo a considerable 
metamorphosis in their development. The largest sea- 
lampreys reach a length of three feet. The common 
brook-lampreys are from eight to twelve inches long only. 

The true fishes (Pisces). — All the other fish-like ani- 
mals are grouped in the class Pisces. They are charac- 
terized, when compared with the lower fish-like forms just 
referred to, by the presence of jaws, shoulder girdle, and 
pelvic girdle. The class includes both the cartilaginous 
and bony fishes, and is divided into three sub-classes, 
namely, the Elasmobranchii, including the sharks, rays, 
skates, torpedoes, etc., the Holocephali, including the 
chimaeras (a few strange-bodied forms), and the Teleos- 
tomi, including all the other fishes, as the trout, catfishes, 
darters, bass, herring, cod, mackerel, sturgeons, etc., etc. 

The sharks, skates, etc. (Elasmobranchii). — The 
sharks and skates are characterized by the possession of 
a, skeleton composed of cartilage and not bone, as in 
the bony fishes; they have no operculum; their teeth 
are distinct, often large and highly specialized, and their 
eggs are few and very large. There are two principal 
groups among Elasmobranchii, viz., the sharks, which 
usually have an elongate body, and always have the gill- 
openings on the sides, and the rays or skates, which have a 
broad flattened body with the gill-openings always on the 
under side. All the members of both groups are marine. 
The sharks are active, fierce, usually large fishes, which 
live in the surface-waters of the ocean and make war on 
other marine animals, all of the species except half a 
dozen being" fish-eaters. The shark's mouth is on the. 



280 ELEMENTARY ZOOLOGY 

under side of the usually conical head, and the animal 
often turns over on its back in order to seize its prey. 
The largest American sharks, and the largest of all fishes, 
are the great basking-sharks {Cetorliinns), which reach a 
length of nearly forty feet. They get their name from 
their habit of gathering in numbers and floating motion- 
less on the surface. They feed chiefly on fishes. 

The hammer-headed sharks {Sphyrna) are odd sharks 
which have the head mallet or kidney shaped, twice as wide 
as long, the eyes being situated on the ends of the lateral 
expansions of the head. The man-eating or great white 
sharks {Car char odon) are nearly as large as the basking- 
sharks, and are extremely voracious. They will follow 
ships for long distances for the refuse thrown overboard. 
They do not hesitate to attack man. Among the more 
familiar smaller sharks are the dog-fishes and sand-sharks 
of our Atlantic coast. 

The rays and skates are also carnivorous, but are with 
few exceptions sluggish, lying at the bottom of shallow 
shore-waters. They feed on crabs, molluscs, and bottom- 
fishes. The small common skates, "tobacco-boxes' 
{Raja erinacea) (fig. 114), about twenty inches long, and 
the larger "barn-door skates' {R. Icevis), are numer- 
ous along the Atlantic coast from Virginia northward. 
Especially interesting members of this group, because of 
the peculiar character of the injuries produced by them, 
are the sting-rays and torpedoes or electric-rays. The 
sting-rays {Dasyatis) have spines near the base of the tail 
w r hich cause very painful wounds. The torpedoes {Narcine) 
have two large electrical organs, one on each side of the 
body just behind the head, with which they can give a 
strong electric shock. "The discharge from a large in- 
dividual is sufficient to temporarily disable a man, and 
were these animals at all numerous they would prove 
dangerous to bathers.' Very different from the typical 



BRANCH CHORD AT A; CLASS PISCES: THE FISHES 281 

rays in external appearance are the saw-fishes {Pristis 
pectinatis), which belong to this group. The body is 
elongate and shark-like, and has a long saw-like snout. 
This saw, which in large individuals may reach a length 
of six feet and a breadth of twelve inches, makes its 
owner formidable among the small sardines and herring- 




Fig. 114. — The common skate, Raja erinacea. (From Kingsley. ) 

like fishes on which it feeds. The saw-fishes live in tropi- 
cal rivers, descending to the sea. 

The bony fishes (Teleostomi). — The bony or true fishes 
are distinguished from the lampreys and sharks and rays 
by having in general the skeleton bony, not cartilaginous, 
the skull provided with membrane bones, and the eggs 
small and many. In this group are included all the 
fishes of our fresh-water lakes, ponds, and streams as well 
as most of the marine forms. Fish life, being spent under 



2 &2 ELEMENTARY ZOOLOGY 

water, is not familiar to most of us, and beginning students 
are rarely helped enough in getting acquainted with the 
different kinds and the interesting habits of fishes. But 
they offer a field of study which is really of unusual interest 
and profit. We can refer in the following paragraphs to 
but few of the numerous common and readily found kinds, 
and to these but briefly. 

Closely related to the sunfish, studied as example of 
the bony fishes, are the various kinds of bass, as the 
"crappie ' {Pomoxis a7imi/aris) y the calico bass (P. sepa- 
roides), the rock-bass (Amblopliies riipestiHs) and the 
large-mouthed and small-mouthed black bass (Micropterus 
sahnoides and M. dolomieu respectively). All the mem- 
bers of this sunfish and bass family are carnivorous fishes 
especially characteristic of the Mississippi valley. 

Another family of many species especially common in 
the clear, swift, and strong Eastern rivers is that of the 
darters and perches. The darters are little slender-bodied 
fishes which lie motionless on the bottom, moving like a 
flash when disturbed and slipping under stones out of sight 
of their enemies. Some are most brilliantly colored, sur- 
passing in this respect all other fresh-water fishes. 

Unlike the sunfishes and darters are the catfishes, 
composing a great family, the Siluridae. The catfish 
(Ameiurus) gets its name from the long feelers about its 
mouth ; from these feelers also come its other names of 
horned pout, or bull-head. It has no scales, but its spines 
are sharp and often barbed or jagged and capable of mak- 
ing a severe wound. 

Remotely allied to the catfish are the suckers, min- 
nows, and chubs, with smooth scales, soft fins and soft 
bodies and the flesh full of small bones. These little fish 
are very numerous in species, some kinds swarming in 
all fresh water in America, Europe, and Asia. They 
usually swim in the open water, the prey of every carniv- 



BRANCH CHORD AT A; CLASS PISCES: THE FISHES 283 



orous fish, making up by their fecundity and their insig- 
nificance for their lack of defensive armature. In some 
species the male is adorned in the spring with bright 
pigment, red, black, blue, or milk-white. In some cases, 
too, it has bony warts or horns on its head or body. Such 
forms are known to the boys as horned dace. 

Most interesting to the angler are the fishes of the 
salmon and trout (fig. 115) family, because they are gamy, 




Fig. 115. — The rainbow-trout, Sal/no iri.ens. (From specimen.) 



beautiful, excellent as food and above all perhaps because 
they live in the swiftest and clearest waters in the most 
charming forests. The salmon live in the ocean most of 
their life, but ascend the rivers from the sea to deposit 
their eggs. The king salmon {Oncorhynchns tscJiawy- 
tscha) of the Columbia goes up the great river more than 
a thousand miles, taking the whole summer for it, and 
never feeding while in fresh water. Besides the different 
kinds of salmon, the black-spotted or true trout, the charr 
or red-spotted trout of various species, the whitefish 
(Coregonus), the grayling {Tliymallus signifer) and the 
famous ayu of Japan belong to this family. 

In the sea are multitudes of fish forms arranged in many 
families. The myriad species of eels agree in having no 
ventral fins and in having the long flexible body of the 
snake. Most of them live in the sea, but the single 



284 ELEMENTARY ZOOLOGY 

genus {Anguilla) or true eel which ascends the rivers is 
exceedingly abundant and widely distributed. Most eels 
are extremely voracious, but some of them have mouths 
that would barely admit a pin-head. The codfish (Gadus 
callarias) is a creature of little beauty but of great useful- 
ness, swarming in all arctic and subarctic seas. The 




Fig. 116. — The winter flounder, Pseadopleuronectes americanus. 

(After Goode.) 

herring {Clupea Jiarengns), soft and weak in body, are 
more numerous in individuals than any other fishes. The 
flounders (fig. 116) of many kinds lie flat on the sea- 
bottom. They have the head so twisted that the two 
eyes occur both together on the uppermost side. The 
members of the great mackerel tribe swim in the open 
sea, often in great schools. Largest and swiftest of these 
is the sword-fish (XipJiias gladius), in which the whole 
upper jaw is grown together to form a long bony sword, 
a weapon of offence that can pierce the wooden bottom 
of a boat. 

Many of the ocean fishes are of strange form and ap- 
pearance. The sea-horses {Hippocampus sp.) (fig. 117) 
are odd fishes covered with a bony shell and with the 
head having the physiognomy of that of a horse. They 
are little fishes rarely a foot long, and cling by their 



BRANCH CHORDA TA; CLASS PISCES: THE FISHES 285 



curved tails to floating seaweed. The pipefish (Syn- 

gnathus fuscitm) is a sea-horse straightened out. The 

porcupine-fishes and swellfishes {Tctraodontidce) have the 

power of filling the stomach 

with air which they gulp from 

the surface. They then escape 

from their pursuers by floating 

as a round spiny ball on the 

surface. The flying-fishes {Exo- 

ccetus) leap out of the water and 

sail for long distances through 

the air, like grasshoppers. They 

cannot flap their long pectoral 

fins and do not truly fly; 

nevertheless they move swiftly 

through the air and thus escape 

their pursuers. In its structure 

a flying-fish differs little from a 

pike or other ordinary fish. 

Foi an account of • the fishes 
of North America see Jor- 
dan's ' 4 Manual of Vertebrates, 
eighth edition, pp. 5— 1 73 ? and 
Jordan and Evermann's " Fishes 
of North and Middle America," 
where the 3.127 species known from our continent are 
described in detail with illustrative figures. 

Habits and adaptations. — The chief part of a fish's life 
is devoted to eating, and as most fishes feed on other 
fishes, all are equally considerably occupied in providing 
for their own escape. 

In general the provisions for seizing prey are confined 
to sharp teeth and the strong muscles which propel the 
caudal fin. But in some cases special contrivances 
appear. In one large group known collectively as the 




Fig. 117.- 
c amp us 
Goode.) 



■A sea-hurse, Hippo- 
kept agonus. (After 



2 86 ELEMENTARY ZOOLOGY 

" anglers " the first spine of the dorsal fin hangs over the 
mouth. It has at its tip a fleshy appendage which serves 
as a bait. Little fishes nibble at this, the mouth opens, 
and they are gone. In the deep seas, many fishes are 
provided with phosphorescent spots or lanterns which 
light up the dark waters, and enable them to see their 
prey. In storms these lantern-fishes sometimes lose their 
bearings and are thrown upward to the surface. 

In general the more predatory in its habits any fish is 
the sharper its teeth, and the broader its mouth. Among 
brook-fishes the pickerel has the largest mouth and the 
sharpest teeth. It has been called a " mere machine for 
the assimilation of other organisms.' The trout has a 
large mouth and sharp teeth. It is a swift, voracious, and 
predatory fish, feeding even on its own kind. The sunfish 
is less greedy and its mouth and teeth are smaller, though 
it too eats other fish. 

As means of escape, most fishes depend on their speed 
in swimming. But some hide among rocks and weeds, 
disguising themselves by a change in color to match their 
surroundings. Others, like the flounders and skates, lie 
flat on the bottom. Still others retreat to the shallows 
or the depths or the rock-pools or to any place safer than 
the open sea. Some are protected by spines which they 
erect w r hen attacked. Some erect these spines only after 
they have been swallowed, tearing the stomach of their 
enemy and killing it, but too late to save themselves. 
Again in some species the spines are armed with poison 
which benumbs the enemy. Sometimes an electric battery 
about the head or on the sides gives the biting fish a 
severe shock and drives him away. Such batteries are 
found in the electric rays or torpedo, in the electric eel 
of Paraguay, the electric catfish of the Nile, the electric 
stargazer and other fishes. 

Some fishes are protected by their poor and bitter flesh. 



BRANCH CHORD AT A: CLASS PISCES: THE FISHES 2, 



Some have bony coats of mail and sometimes the coat of 
mail is covered with thorns, as in the porcupine-fish. 
This fish and various of its relatives have the habit of filling 
the stomach with air when disturbed, then floating belly 
upward, the thorny back only within reach of its enemies. 
Many species (cling fishes) attach themselves to the 
rocks by a fleshy sucking-disk. Some [Reword) (fig. 1 1 8) 
cling to larger fishes by a strange sucking-disk on the head, 
a transformed dorsal fin, being thus shielded from the 




Fig. 118. — The remora, or cling fish, Remoropsis brachyptera. Note sucker 
on top of head. (After Goode.) 

attacks of fish smaller than their protectors. Some small 
fishes seek the shelter of the floating jellyfishes, lurking 
among their poisoned tentacles. Others creep into the 
masses of floating gulf-weed. Some creep into the shell 
of clams and snails. In the open channel of a sponge, 
the mouth of a tunicate and in similar cavities of various 
animals, little fishes may be found. A few fishes (hag- 
fishes) are parasitic on others, boring their way into the 
body and devouring the muscles with their rasp-like 
teeth. 

Some fishes are provided with peculiar modifications of 
the gills which enable them to breathe for a time out of 
water. Such fish have the pectoral fins modified for a 
rather poor kind of locomotion on land, thus enabling 
them to move from pond to pond or from stream to stream. 
In cold climates the fishes must either migrate to warmer 
latitudes in winter, as some do, or withstand variously the 
cold, often freezing weather. Some fish can be frozen 



288 ELEMENTARY ZOOLOGY 

solid, and yet thaw out and resume active living. Some 
lie at the bottoms of deep pools through the colder periods, 
while many others, such as the minnows, chubs, and 
other kinds common in small streams, bury themselves in 
the mud, and lie dormant or asleep through the whole 
winter. On the other hand in countries where the long 
intense rainless summers dry up the pools, some fishes 
have the habit of burying themselves in the mud, which, 
with slime from the body, forms about them a sort of tight 
cement ball in which they lie dormant until the rains 
come. M Thus a lung-fish (called Protopteriis), found in 
Asia and Africa, so completely slimes a ball of mud 
around it that it may live for more than one season, per- 
haps many; it has been dug up and sent to England, still 
enclosed in its round mud-case, and when it was placed 
in warm water it awoke as well as ever. ' ' 

Food-fishes and fish-hatcheries. — Most fishes are suit- 
able for food, though not all. Some are too small to be 
worth catching or too bony to be worth eating, Some 
of the larger ones, especially the sharks, are tough and 
rank. A few are bitter and in the tropics a number of 
species feed on poisonous coelenterates about the coral 
reefs, becoming themselves poisonous in turn. But a fish is 
rarely poisonous or unwholesome unless it takes poisonous 
food. Where fishes of a kind specially used for food gather 
in great numbers at certain seasons of the year, fishing is 
carried on extensively and with an elaborate equipment. 
Such fisheries, some of which have been long known, are 
scattered all over the world. Along the shores of the 
Mediterranean Sea, and on the coasts of Norway, France, 
the British Isles and Japan are numerous great fishing- 
places. But " nowhere are there found such large fisheries 
as those along the northern Atlantic coasts of our own 
continent, extending from Massachusetts to Labrador. 
Especially on the banks of Newfoundland are codfish, 



BRANCH CHORD AT A: CLASS PISCES: THE FISHES 289 

herring, and mackerel caught. '' Among our fresh-water 
fisheries the great salmon fisheries of the Penobscot and 
Columbia rivers and of the Karluk and other rivers of 
Alaska are the best known. The whitefish of our Great 
Lakes is also one of the important food-fishes of the world. 

In many places fishes are raised in so-called hatcheries, 
not usually for immediate consumption but for the purpose 
of stocking ponds and streams either in the neighborhood 
of the hatchery or in distant waters which the special 
species cultivated has not been able naturally to reach. 
The eggs of some fishes are large and non-adherent, two 
features which greatly favor artificial impregnation and 
hatching. In the hatcheries the eggs are put first into 
warm water, where development begins; they are then 
removed into cool water, which arrests development with 
out injury, making shipment possible. The eggs of 
salmon and trout in particular can be sent long distances 
to suitable streams or ponds. The eggs of the shad have 
been thus carried from the East to the streams of Cali- 
fornia and trout have been distributed to many streams in 
our country which by themselves they could never have 
reached. 

The salmon is a conspicuous example of those fishes 
which can be artificially propagated. The eggs of the 
salmon are large, firm, and separate from each other. If 
the female fish be caught when the eggs are ripe and 
her body be pressed over a pan of water the eggs will 
flow out into the water. By a similar process the milt or 
male sperm-cells can be procured and poured over the 
eggs to fertilize them. The young after hatching are kept 
for a few days or weeks in artificial pools, till the yolk- 
sacs are absorbed and they can take care of themselves. 
They are then turned into the stream, where they drift tail 
foremost with the current and pass downward to the sea. 
All trout may be treated in similar fashion, but there are 



2 9o ELEMENTARY ZOOLOGY 

many food-fishes which cannot be handled in this way. 
In some the eggs are small or soft, or viscid and adhering 
in bunches. In others the life-habits make artificial fer- 
tilization impossible. Such species are artificially reared 
only by catching the young and taking them from one 
stream to another. To this type belong the black bass, 
the sunfish, the catfish and other familiar forms. 



CHAPTER XXV 

BRANCH CHORDATA (Continued). CLASS BA- 
TRACHIA: THE BATRACHIANS 

The structure, life-history, and habits of the garden- 
toad (Bufo lentiginosus) have already been studied (see 
Chapter II and Chapter XII). 

OTHER BATRACHIANS. 

The class Batrachia includes the animals familiarly 
known as ccecilians, sirens, mud-puppies, salamanders, 
toads, and frogs. Although differing plainly from fishes 
in appearance and habits, the batrachians are really closely 
related to them, resembling them in all but a few essential 
characters. Among the distinctive characters of ba- 
trachians may be noted the absence of fins supported 
by fin-rays, the presence usually of well-developed legs 
for walking or leaping, and the absence or reduction of 
certain bones of the head connected with the gills and 
lower jaw and which are well developed in the fishes. 
The batrachians stand in somewhat intermediate position 
between the fishes and the reptiles, showing some of the 
characters of both. They are, like fishes and reptiles, 
cold-blooded. In their adult condition some are terres- 
trial and some aquatic as to habitat, but all have an aquatic 
larval life. The water-inhabiting young breathe at first 
by means of gills, later lungs begin to develop, and for a 
time both gills and lungs are used in respiration. Finally 
in the adult condition in almost all of the forms the gills 

291 



292 ELEMENTARY ZOOLOGY 

are wholly lost and breathing is done by the lungs and 
skin solely. Correlated with the change of habits from 
larval to adult stage there is usually a well-marked meta- 
morphosis in post-embryonic development. This meta- 
morphosis is specially striking among the frogs and toads. 
None of the aquatic forms is marine, salt water always 
killing eggs, larvae or adults. Batrachians are found all 
over the world, although there are few in the extreme 
North. They are most abundant in warm and tropical 
lands. 

Body form and organization. — The body varies from 
a long and slender, truly snake-like form as in the tropical 
coecilians through the usual salamander (fig. 119) shape, 
where it is more robust but still elongate and tailed, to 
the heavy, squat, tailless condition of the toads. Legs, 




Fig. 119.— The tiger salamander. (From Jenkins and Kellogg.) 

with five digits, are usually present, and are used for 
swimming, walking, or leaping. The legs are longest 
and best developed in the short tailless frog and toad 
forms which are mostly terrestrial, and are short and weak 
in the tailed salamander forms, many of which are aquatic. 
The skin is almost always naked, showing a marked differ- 
ence from the scaled condition of reptiles and most of the 
fishes, and its cells secrete a slimy, sticky, usually whitish 
fluid, which in some cases is irritating, or even poisonous. 



BRANCH CHORD AT A : CLASS BATRACHIA -93 

The skin is sometimes thrown up into folds or ridges, and 
in some species is elevated to form a kind of fin on the 
tail or back. This unpaired fin differs from the dorsal fin 
(and other fins) of fishes in not being supported by rayed 
processes of the skeleton. There are in some batrachians 
traces of an exoskeleton in the presence of scale-like 
structures in the skin or in the horny nails on the digits, 
but these cases are rare. The skin contains pigment-cells 
and many of the batrachians are brilliantly colored and 
patterned; some of the pigment is carried by special con- 
tractile or expansile cells, the chromatophores (see 
account of chromatophores of the Cephalopoda, p. 256), 
so that the animal can change its tint and markings more 
or less rapidly. All the batrachians possess external gills 
in their aquatic larval stage, and in a few forms, as the 
sirens and mud-puppies, gills are retained all through life. 
These gills are branched folds of the skin abundantly 
supplied with blood-vessels. 

In the organization of the batrachian body the usual 
vertebrate characters appear, the body-organs being 
arranged with reference to a supporting and protecting 
internal bony skeleton. The head is plainly set off from 
the rest of the body and bears the mouth and the organs 
of hearing and sight. Certain so-called lateral sense 
organs, the function of which is not exactly known, occur 
arranged in three lines on each side of the body of some 
of the forms. Both pairs of limbs are present and func- 
tional in almost all of the species. In the coecilians the 
limbs are wholly wanting ; in the sirens only the fore legs 
are present. 

Structure. — The most obvious skeletal differences 
among batrachians are those due to variations in external 
form. While there are as many as 100 vertebras in some 
of the elongate long-tailed salamanders (even 250 in the 
strange snake-like coecilians), there are but 10 (the last 



294 ELEMENTARY ZOOLOGY 

or tenth being the rod-shaped bone called the urostyle) 
in the short, tailless frogs and toads. To any of the 
vertebrae except the first (the single cervical vertebra) and 
the last, ribs may be attached and the coecilians have 
about as many pairs of ribs as vertebrae. In the frogs 
and toads, however, the ribs are lost. In any case they 
are never fastened by their lower ends to the breast-bone. 

The alimentary canal is usually not much longer than 
the body and is plainly divided into mouth, pharynx, 
oesophagus, small intestine, large intestine or rectum, 
and anal opening. The teeth when present occur on both 
the jaws and the palate. They are small, sharp, point 
backward and are fused to the bones. They are wholly 
wanting in the toad and in some other allied forms. The 
tongue may be wanting, or may be immovably fixed to 
the floor of the mouth, or as in the frogs, fastened at its 
front end but free behind, so that the hinder end can be 
protruded far from the mouth for the purpose of catching 
insects. 

The organs of respiration are gills, external and in- 
ternal, lungs, trachea or windpipe, and the skin. In the 
earliest larval stages all batrachians have gills; later, in 
most cases, the gills become reduced and disappear, while 
at the same time lungs are developing. In some sala- 
manders the lungs never develop, but the animals, in their 
adult stage, breathe wholly by means of the skin. In a 
few cases, as in the siren and mud-puppies, gills are 
retained through the whole life, although lungs are also 
present in the adult stage. The lungs are two in number, 
a right and a left lung, and are simple sacs with the walls 
more or less folded or thrown into ridges and richly sup- 
plied with blood-vessels. The front end of the lungs 
opens directly into the pharynx or, in the more elongate 
batrachians, is connected with it by a tubular trachea or 
windpipe. In the frogs and toads there are vocal cords 



BRANCH CHORD AT A: CLASS BATRACHIA 295 

stretched across the short windpipe; the vibration of 
these cords produces the croaking. 

The heart is always three-chambered, consisting of the 
right and left auricles and a single ventricle. The circu- 
lation of the more generalized salamanders like the mud- 
puppies is essentially like that of a fish. In the frogs and 
toads there is a distinct advance beyond this condition. 
The red corpuscles of the blood are oval in shape and are 
the largest found among any of the vertebrates. 

In the nervous system the small size of the hindbrain 
or cerebellum is noticeable. The sense organs are fairly 
well developed. The skin of the whole body is provided 
with tactile nerve-endings. There are special taste organs 
on the lining membrane of the tongue and mouth-cavity. 
The eyes have no lids in some of the lower forms; most 
of the frogs and toads have an upper lid but no under one, 
although a thin membrane, called the nictitating mem- 
brane, arises from the lower margin of the eye and can be 
drawn up over it. The ears have no external parts, other 
than the thin tympanic membranes. The nostrils of frogs 
and toads can be closed by the contraction of certain 
special muscles. 

Life-history and habits. — The sexes are distinct, and in 
most cases the young hatch from eggs. A few of the sala- 
manders give birth to free young. The eggs are usually in 
strings or chains enclosed in a clear gelatinous substance ; 
these chains of eggs are either simply dropped into the 
water or are fastened to water-plants. The young, called 
tadpoles (fig. 120), in their earlier larval stages are ex- 
tremely fish-like in character, long-bodied, tailed, swim- 
ming freely about by means of the fin-like flattened tail, and 
breathing by means of external gills. Nor do they show 
any sign of legs. As the tadpoles grow and develop the 
legs begin to appear, the hind legs first in the frogs and 
toads, the fore legs first in the salamanders ; lungs develop 



296 ELEMENTARY ZOOLOGY 

and the gills disappear (except in the cases of the few forms 
which retain gills through life). The tail shortens and 
finally disappears in the frogs and toads ; with the salaman- 
ders the tail-fin only is lost. At the same time the change 
from water to land is made. Further growth is very 




Fig. 120. — Tadpoles. (Photograph from life by Cherry Kearton; per- 
mission of Cassel & Co.) 

slow; frogs are not really adult, that is, capable of pro- 
ducing young, until they are five years old, and they may 
continue to increase in size until they are ten years old. 

The food of the adult batrachians is almost exclusively 
small animals, particularly insects and worms. Crus- 
taceans, snails, and young fish are also eaten. The tad- 
poles also eat vegetable matter. Almost all batrachians 
are nocturnal in habit, remaining concealed by day. In 
the zones in which cold winters occur they hibernate or 
pass the winter in a torpid condition, or state of "sus- 
pended animation," or, as it is said, they sleep through 
the winter. Frogs burrow into the mud at the bottom of 
ponds at the approach of winter and come forth early in 



BRANCH CHORD AT A: CLASS BAT RA CHI A 297 

the spring to lay their eggs. Most batrachians are very 
tenacious of life, being able to withstand long periods of 
fasting and serious mutilation, and most of them can 
regenerate certain lost parts, such as the tail or legs. 

Classification, — The living Batrachia are divided into 
three orders, viz., the Urodela, including the sirens, mud- 
puppies, salamanders, and newts, batrachians which retain 
the tail throughout life, having generally two pairs of limbs 
of approximately equal size, and sometimes possessing 
gills or gill-slits in the adult condition; the Anura, or 
frogs and toads, with no tail in the adult condition, with 
short and broad trunk, with hind limbs greatly exceeding 
the fore limbs in size, and never with gills or gill-slits 
in the adult stage ; and the Gymnphiona, or coecilians, 
snake-like batrachians having neither limbs nor tail, with 
a dermal exoskeleton and without gills or gill-slits in the 
adult. 

Mud-puppies, salamanders, etc. (Urodela). — Techni- 
cal Note. — If possible obtain specimens of mud-eels (Siren), com- 
mon in the South, or mud-puppies [Necturus), common in the cen- 
tral North, as examples of batrachians with gills persisting in the 
adult stage. One or more species of Amblystonia may be found in 
almost any part of the country, and larvae of large size may be found 
with the external gills. For an example of the general long-tailed 
or Urodelous type of batrachian any salamander or newt occurring 
in the vicinity of the school may be used. The little green triton or 
eft (Diemyctylns viridiscens) of the eastern States, or its larger 
brown-backed congener of the Pacific coast (D. torosus) is common 
in water, while another eft, the little red-backed salamander, 
(Plethodon) is common in the woods under logs and stones. The 
external characters of the body should be compared with those of 
the toad. The skeleton should be prepared by macerating away 
the flesh (for directions, see p. 452), and the presence of the many 
caudal vertebrae and the ribs, the equality in size of the legs, and 
other points should be noted. Compare w T ith skeleton of toad. 
Make drawings. It will be well, also, to dissect out and examine 
the various internal organs of the salamander, comparing them with 
the same organs in the toad. The salamander, indeed, is in many 
ways better than the toad as an example of the class. Its body is 
less adaptively modified and shows the essentially fish-like charac- 
ter of the batrachian structure. 



298 ELEMENTARY ZOOLOGY 

The batrachians which retain external gills in the adult 
stage are the members of two families of which the 
American representatives are known as mud-eels [Siren) 
and mud-puppies or water-dogs {Necturus). The mud- 
eels, which are found "in the ditches in the swamps of 
the southern States from South Carolina to the Rio Grande 
of Texas and up the Mississippi as high as Alton, Illinois," 
are blackish in color, have no hind legs and are long and 
slender, with the tail shorter than the rest of the body. 
They reach a length of nearly three feet. The mud- 
puppies, found in the Great Lakes and in the rivers of the 
upper Mississippi valley, are brown with colored spots, 
and are about two feet long when full grown. They have 
both fore and hind legs. 

A few salamanders, while not possessing external gills 
when adult, have a spiracle or small circular opening in 
the side of the neck which leads into the throat. The 
best-known American salamander of this kind is the 
large heavy-bodied blackish water-dog or ' ' hellbender ' 
{Cryptobranchus) of the Ohio River. It is about two feet 
long, and is "a very unprepossessing but harmless 
creature.' It has a conspicuous longitudinal fold of skin 
along each side of the body. The largest known ba- 
trachian, the giant salamander of Japan (MegalobatracJius), 
reaching a length of three feet, is related to the water- 
dog. 

Of all the salamanders the most interesting are the 
blunt-nosed salamanders {Amblystoma). A dozen or 
more species of Amblystoma occur in North America, of 
which tigrimim, a dark-brown species with many irregular 
yellow blotches sometimes arranged in cross-bands, is the 
most widespread. The larvae of some Amblystoma retain 
their gills until they have reached a large size, and in one 
or two species the usual metamorphosis is very long 
delayed and the salamanders produce young while in the 



BRANCH CHORD AT A: CLASS BATRACHIA 299 

larval condition, that is, while retaining the gills and a 
compressed fin-like tail. In the case of a certain Mexican 
species (A. maadatum) it is believed that the final meta- 
morphosis never occurs. The Mexicans call these gilled 
larval Ambly stoma axolotls, and use them for food. For 




Fig. 121. — The Western brown eft, or salamander, Diemyctyhis torosus. 

(From living specimen.) 

a long time naturalists supposed the Ambly stoma larvae 
which produce young to be the adults of a species of sala- 
manders which retained their gills through life, like the 
sirens and mud-puppies, and classified them in a distinct 
genus. 

Of the various common salamanders or newts some are 
found in streams, ponds, and ditches, and some under 
logs and stones in the woods. The aquatic forms have 
the tail compressed (flattened from side to side), while 
the land forms have the tail cylindrical, tapering to a 
point. Most of the land-salamanders produce their young 
alive, while the water forms lay eggs which are usually 
attached to a submerged plant-stem. The salamanders 
are, almost without exception, found only in the northern 
hemisphere. 

Frogs and toads (Anura). — There are about a dozen 
species of frogs in the United States. The largest of 
these, and indeed the largest of all the frogs, is the well- 
known bullfrog {Rana catesbiana), which reaches a length 
(head to posterior end of body) of eight inches. It is 
found in ponds and sluggish streams all over eastern 



300 ELEMENTARY ZOOLOGY 

United States and in the Mississippi valley. It is green- 
ish in color with the head usually bright pale green. Its 
croaking is very deep and sonorous. The pickerel-frog 
{R. palustris), which is bright brown on the back with two 
rows of large oblong square blotches of dark brown on 
the back, is found in the mountains of eastern United 
States. The little pale reddish-brown wood-frog [R. syl- 
vatica) with arms and legs barred above is common in 
damp woods and is "an almost silent frog.' The 
peculiar and infrequently seen frogs known as the 4 i spade- 
foots ' ' (Scaphiopus) are subterranean in habit and usually 
live in dry fields or even on arid plains and deserts. 
They pass through their development and metamorphosis 
very rapidly, appearing immediately after a rain and lay- 
ing their eggs in temporary pools. At this time of egg- 
laying they utter extraordinarily loud and strange cries. 
Some frogs in other parts of the world live in trees, and 
the eggs of one species are deposited on the leaves of 
trees, leaves which overhang the water being selected so 
that the issuing young may drop into it. 

The true tree-frogs or tree-toads (Hylidse) constitute a 
family especially well represented in tropical America. 
They have little disk- or pad-like swellings on the tips of 
their toes to enable them to hold firmly to the branches 
of the trees in which they live. Some, like the swamp 
tree-frog and the cricket-frog, are not arboreal in habit, 
remaining almost always on the ground. The common 
tree-frog of the eastern States {Hyla versicolor) is green, 
gray, or brown above with irregular dark blotches, and 
yellow below. It croaks or trills, especially at evening 
and in damp weather. Pickering's tree-frog {Hyla 
pickeringii) makes the "first note of spring' in the 
eastern States. This tree-frog is the one most frequently 
heard in the autumn too, but "its voice is less vivacious 
than in the spring and its lonely pipe in dry woodlands is 



BRANCH CHORD AT A: CLASS BATRACHIA 301 

always associated with goldenrods and asters and falling 
leaves. ' : The tree-frogs of North America lay their eggs 
in the water on some fixed object as an aquatic plant, in 
smaller packets than those of the true frogs, and not in 
strings as do the toads. 

The toads (Bufonidae) differ from the true frogs in 
having no teeth and in not having, as the frogs do, a 
cartilaginous process uniting the shoulder-bones of the 
two sides of the body. The absence of this uniting 
process makes the thoracic region capable of great expan- 
sion. There are only a few species of toads in North 
America, but one of these species, the common American 
toad (Bnfo lentiginosiis), is very abundant and wide- 
spread. It appears also in two or three varieties, the 
common toad of the southern States differing in several 
particulars from that of the northern. The toad is a 
familiar inhabitant of gardens, and does much good by 
feeding on noxious insects. It is most active at twilight. 
Its eggs are laid in a single line in the centre of a long 
slender gelatinous string or rope, which is nearly always 
tangled and wound round some water-plant or stick near 
the shore on the bottom of a pond. The eggs are jet 
black and when freshly laid are nearly spherical. At the 
time of egg-laying the toads croak or call, making a sort 
of w T histling sound and at the same time pronouncing deep 
in the throat li bu-rr-r-r-r. ' The toad does not open its 
mouth when croaking, but expands a large sac or resonator 
in its throat. The toad-tadpoles are blacker than those 
of frogs or salamanders, and undergo their metamorphosis 
while of smaller size than those of frogs. When they 
leave the water they travel for long distances, hopping 
along so vigorously that in a few days they may be as far 
as a mile from the pond where they were hatched. They 
conceal themselves by day, but will appear after a warm 
shower; this sudden appearance of many small toads 



3° 2 ELEMENTARY ZOOLOGY 

sometimes gives rise to the false notion that they have 
fallen with the rain. 

Coecilians (Gymnophiona). — The third order of ba- 
trachians, the coecilians, includes about twenty species of 
slender worm- or snake-like limbless forms which are 
confined to the tropics. Some of them are wholly blind 
and the others have only rudimentary eyes. In them the 
skin is folded at regular intervals so that the body appears 
to be rigid or segmented, and in some species there are 
small concealed horny scales in the skin. 



CHAPTER XXVI 

BRANCH CHORDATA {Continued^. CLASS REP- 
TILIA: THE SNAKES, LIZARDS, TURTLES, 
CROCODILES, ETC. 

THE GARTER SNAKE (Thamnophis sp.) 

TECHNICAL Note. — Garter snakes may be found almost any- 
where during the spring and summer months. If possible each 
student should have a specimen, but in case it is difficult to get 
enough snakes two students can use a single specimen. If garter 
snakes are rare, take any other snake. Snakes will live a long time 
without feeding and specimens should be kept alive until ready to 
use. Kill with chloroform as directed for the toad (p. 5). After 
completing the study of the external characters place each specimen 
in a dissecting-pan and with a pair of scissors cut through the scales 
on the ventral side, passing backwards from the eighteenth to the 
fortieth. Pin back the edges of the cut and thus expose the heart. 
Through its lower end, the ventricle, insert a large canula; inject 
with a fairly large syringe the glue mass which is described on 
p. 452. This injection wall fill the entire arterial system. To inject 
the venous system make another cut through the ventral scales, cut- 
ting forward from the anal scale through about forty of them. Note 
the injected mass in some of the vessels already tilled. Take one 
of the large vessels still containing blood and pass two ligatures 
beneath it. Get ready a small canula and cut a slit in the vessel, 
elevating the head so that the blood will run out as much as possi- 
ble. Now w T ash the blood off, insert the canula in the slit and tie 
one ligature about the vessel containing the canula ; have the other 
ready to tie after the vein has been injected. Use a new color for 
the venous system. Leave specimen in cold water for a time until 
the injection is hard. Then continue the cut from the anal plate 
forward to the lower jaw and pin out the edges of the cut on both 
sides in the dissecting-pan. 

Structure (fig. 122). — Note that the snake is covered 
with horny scales somewhat as the fish is. How do these 
scales differ from those of the fish ? In snakes the scales 

303 



3°4 ELEMENTARY ZOOLOGY 

are not bony, but are true skin structures. Note the modi- 
fication of the scales on the head, back, and ventral sur- 
face. Those on the dorsal surface often have minute 
ridges, the keels. How do the ventral scales differ from the 
dorsal ones and others ? By a system of muscles these 
ventral scales are rhythmically moved and as their posterior 
edges are pushed back against some resisting object the 
body glides forward. On the head note the pair of eyes. 
Are there eyelids ? In front of each eye note an opening. 
What are these openings ? Thrust a bristle into the 
opening and see where it enters the mouth-cavity through 
the internal nares. Does the snake have external ears ? 
Observe the very long Jaws and note that they are loosely 
hinged. Examine the inside of the mouth. Are there 
teeth ? If so where are they situated, and how arranged? 
Note that all of the teeth point backwards. Food is not 
chewed. When some object of prey, a frog, or mouse, 
for example, is seized, the teeth hold it fast to the roof of 
the mouth and by a backward and forward movement of 
the lower jaws it is gradually drawn into the large 
oesophagus. What is the character and situation of the 
tongue ? Just behind the tongue note the narrow slit, 
glottis, opening into the windpipe, or trachea. Back of 
the trachea opens the oesopliagus. 

When the snake is laid open the elongate heart will 
be conspicuous in the anterior third of the body. Insert 
a blowpipe or quill into the glottis just back of the tongue, 
and inflate the lung, which is a long, thin-walled bag 
extending from the region of the heart posteriorly for 
two-thirds of the length of the body. There is but one 
developed lung, the right; note at the anterior end of the 
lung a small mass of tissue, the atrophied left lung. 
Running forward from the lung is a long tube composed 
of incomplete cartilaginous rings, connected by mem- 
brane, the trachea. Note the long straight alimentary 



BRANCH CHORD AT A: CLASS REPTILIA 305 

canal. Distinguish the oesophagus, stomach, intestine, 
rectum and the anus. 

In the region of the lung is an elongated dark-red 
glandular mass, the liver. The secretion from the liver 
passes down through the long hepatic duct to the oval- 
shaped green gall-bladder and into the intestine. 

Technical Note. — The bile-duct may be injected through the 
gall-bladder with some colored injecting mass. 

Note that the duct running off from the gall-bladder to 
the intestine passes through a pink glandular organ, the 
pancreas. At the anterior end of the pancreas is a dark- 
red nodular structure, the spleen. The alimentary canal, 
the liver and the spleen are all suspended from the dorsal 
wall of the body-cavity by a delicate sheet of tissue. 
What is this ? This condition we have also noted in the 
toad and fish. 

Toward the posterior end of the body cavity are two 
long, dark-red glands, the kidneys, which are the prin- 
cipal excretory organs of the body. Through a long, 
slender tube (the ureter) each of the kidneys passes off its 
wastes. Where do the ureters open ? 

Anterior to the kidneys are the reproductive organs. 
The eggs, produced by the female snake, after being 
fertilized, pass backward through the egg-tubes. During 
the breeding season these tubes are much distended. 
This is due to the presence of the developing eggs, for 
the young snakes are hatched in the egg-tubes. 

A successful injection as directed in the first technical 
note will have filled both arterial and venous systems. 
How does the general shape of the snake's heart compare 
with that of the toad ? The heart consists of two ven- 
tricles, incompletely separated, and two auricles. In the 
snake the conus arteriosus is very much shortened and is 
not visible. Note two large vessels arising from the 



306 ELEMENTARY ZOOLOGY 

median portion of the ventricle. The one on the left side 
is the left aortic artery or left aortic arch, while the right 
gives off two branches. Where does the anterior one of 
these run ? The main branch, or right aortic arch, passes 
back to meet its fellow, the left aortic artery, forming with 
it the dorsal aorta, which runs posteriorly to the end of the 
tail. Note the various branches given off by the dorsal 
aorta and trace some of them. Arising from the ventricles 
beneath the two aortic arches is the pulmonary artery, 
which goes to the lung. There the blood is purified, after 
which it is taken up by the pulmonary vein and carried 
back to the left auricle, whence it passes into the ventricle 
to be mixed with the impure blood from the right auricle. 
From the arteries the blood flows to all parts of the body 
through fine capillaries, bathing the tissues, giving off 
oxygen and taking up the carbonic acid gas. From these 
capillaries it passes into veins and so back to the heart; 
from the anterior end of the body through the jugular 
veins and from the posterior portion of the body through 
the postcaval vein. Flowing forward from the tail in the 
caudal vein, the blood enters the capillaries of the kidneys, 
where the waste matter is taken from it. This part of the 
circulatory system is known as t\\tre7tal-portalc\rcu\di\Aon. 
From the kidneys the blood flows through the postcaval 
vein anteriorly to the heart. 

The blood which passes out from the dorsal aorta to all 
parts of the alimentary canal is again collected into veins 
which unite to form the mesenteric vein. This vein runs 
to the liver, where it breaks up into capillaries. Thence 
the blood is carried into the postcaval vein, which leads 
directly to the heart. This part of the circulatory system 
which collects blood from the alimentary canal and carries 
it to the liver is called the hepatic-portal system. 

Just in front of the heart will be noted a nodular struc- 
ture, the thyroid gland, while a little in advance of the 



BRANCH CHORD AT A: CLASS REPTILIA 307 

thyroid may be seen a long glandular mass, the thymus 
gland. The functions of these glands are not certainly 
understood. 

Remove the alimentary canal and muscles from a part 
of the body and note that the axial skeleton, like that of 
the other vertebrates studied, consists of a series of verte- 
bra placed end to end. Are there arms or legs ? Are 
shoulder and pelvic girdles present ? How many of the 
vertebrae bear ribs ? The ribs connect at their lower ends 
with the ventral scales. Note the great number of the 
vertebrae and ribs as compared with those of the toad or 
fish. What are those vertebrae called which bear no ap- 
pendages or ribs ? Examine carefully the elongated skull 
of the snake, especially the modified jaws. A detailed 
study of the skeleton may be made by referring to 
the account of the skeleton of the lizard in Parker's 
' 'Zootomy," pp. 130 et seq. 

The nervous system may be worked out in a specimen 
which has been immersed in 20 per cent nitric acid. The 
description of the nervous system of the toad (see pp. 12— 
13) will suffice for a guide to the study of the nervous 
system of the snake. The special sense organs, as eyes 
and ears, should be examined and compared with those 
of the fish and toad. 

Life-history and habits. — The garter snakes are more 
or less aquatic in habit and are good swimmers. They 
are often found far from water, but in greatest abundance 
where the cat-tails and rushes grow thickest, They feed 
on frogs, salamanders, and field-mice, which they swallow 
whole. All the garter snakes are ovoviviparous, i.e., 
hatch eggs within the body-cavity. The eggs, often as 
many as eighteen or twenty, are enclosed within widened 
portions of the oviducts during embryonic existence; when 
the young are born they are able to shift for themselves. 
During cold weather the garter snake hibernates, hiding 



308 ELEMENTARY ZOOLOGY 

then in some gopher-hole, or, in the warmer climates, 
under some log or stone, there to lie dormant until the 
warm days of spring come, when it resumes activity. 

The garter snake sheds its skin at least once a year, 
sometimes oftener. This process may be observed in 
snakes kept in confinement. For some time before molt- 
ing the animal remains torpid, the eyes become milky, 
and the skin loses its lustre. After a few days it conceals 
itself, the skin about the lips and snout pulls away and the 
animal slips out of its entire skin. The snake not only 
sheds the skin of the body but also the covering of the 
eyes. Snakes have no eyelids, as we have already noted, 
that which represents the eyelid being a transparent 
membrane which covers the eyeball. 

No species of the garter snake group is poisonous. 
Sometimes a garter snake may appear to be vicious, but 
its teeth are very short and at best it can only make a 
small scratch scarcely piercing the skin. 

OTHER REPTILES. 

The class Reptilia includes the lizards, snakes, tortoises, 
turtles, crocodiles, and alligators. Although popularly 
associated in the common mind with the batrachians, the 
reptiles are really more nearly related to the birds than 
to the salamanders and frogs. In general shape they 
more nearly resemble the batrachians, but in the structural 
condition of the internal body organs they are more like 
the birds. They are cold-blooded, and breathe exclu- 
sively by means of lungs, the forms which live in water 
coming to the surface to breathe. They are covered with 
horny scales or plates, which with the entire absence of 
gills after hatching readily distinguish them from all the 
batrachians. While most reptiles live on land, some in- 
habit fresh water and some the ocean. As the young 



BRANCH CHORD AT A: CLASS REPTlLlA 



3°9 



have the same habitat and general habits as the adult, 
there is no such metamorphosis in their life-history as is 
shown by the batrachians. The reptiles are widespread 
geographically, occurring, however, in greatest abund- 
ance in tropical regions, and being wholly absent from the 
Arctic zone. They are not capable of such migrations 
as are accomplished by the birds and many mammals, 
but withstand severely hot or cold seasons by passing into 
a state of suspended animation or seasonal sleep or torpor. 



I* - 

in 




Fig. 123. — A lizard in the grass. (Photograph from life by Cherry Kear- 
ton; permission of Cassell & Co.) 

Body form and organization. — The chief variations in 

body form among the reptiles are manifest when a turtle, 

lizard, and snake are compared. In the turtles, the body 

is short, flattened, and heavy, and provided always with 

four limbs, each terminating in a five-toed foot; in the 

lizards the body is more elongate and with usually four 

legs, but sometimes with two only, or even none at all; 

while in the snakes the long, slender, cylindrical body is 

legless or at most has mere rudiments of the hinder limbs. 

With the reptiles locomotion is as often effected by the 

bending or serpentine movements of the trunk as by the 

use of legs. Among lizards and snakes the body is 

covered with horny epidermal scales or plates, while 



3 IQ ELEMENTARY ZOOLOGY 

among the turtles and crocodiles there may be, in addition 
to the epidermal plates, a real deposit of bone in the skin 
whereby the effectiveness of the armor is increased. The 
epidermal covering of snakes and lizards is periodically 
molted, or, as we say, the skin is shed. The bright colors 
and patterns of snakes and of many lizards are due to the 
presence and arrangement of pigment-cells in the skin. 
Among some reptiles, notably the chameleons, the colors 
and markings can be quickly and radically changed by 
an automatic change in the tension of the skin. 

Structure. — In reptiles, as in batrachians, the chief 
variations in the body skeleton are correlated with differ- 
ences in external body form. In the short compact body 
of the turtles and tortoises the number of vertebrae is much 
smaller than in the snakes. Some turtles have only 34 
vertebrae; certain snakes as many as 400. The reptilian 
skull, in the number and disposition of its parts and in the 
manner of its attachment to the spinal column, resembles 
that of the birds, although the cranial bones remain sep- 
arate, not fusing as in the birds. In the snake the two 
halves of the lower jaw are not fused in front but are 
united by elastic ligaments, which condition, together 
with the extremely mobile articulation of the base of the 
jaws, allows the snakes to open their mouths so as to take 
in bodies of great size. All of the reptiles, except the 
turtles, are provided with small teeth which serve, gen- 
erally, for seizing or holding prey and not for mastication. 
The poisonous snakes have one or more long, sharp, and 
grooved or hollow fangs (fig. 131). In the legless reptiles 
both shoulder and pelvic girdles may be wholly lacking; 
in the limbed forms both girdles are more or less well 
developed. 

The tongue of many reptiles, notably the snakes, is 
bifid or forked, and is an extremely mobile and sensitive 
organ. The oesophagus is long and in the snakes can be 









5- 






-^ 


5$ 






g 

*3 


— >* 


1 


CO 


^ 


'«** 




^ 


*i 






•< 



"T3 
"Si 







^ 



in 



u 

o 



'J 



BRANCH CHORD AT A: CLASS REP TI LI A 3 11 

stretched very wide so as to permit the swallowing of 
large animals whole. Reptiles breathe solely by lungs, 
of which there is a pair They are simple and sac-like, 
the left lung being often much smaller than the other. 
In turtles and crocodiles the lungs are divided internally 
by septa into a number of chambers. Because of the 
rigidity of the carapace or " box " of turtles the air cannot 
be taken in the ordinary way by the use of the ribs and 
rib-muscles, but has to be swallowed. The reptilian heart 
consists of two distinct auricles and of two ventricles, 
which in most reptiles are only incompletely divided, the 
division into right and left ventricles being complete only 
among the crocodiles and alligators, the most highly 
organized of living reptiles. 

The organs of the nervous system reach a considerable 
degree of development in the animals of this class. The 
brain in size and complexity is plainly superior to the 
batrachian brain and resembles quite closely that of birds. 
Of the organs of special sense those of touch are limited 
to special papilhe in the skin of certain snakes and many 
lizards. Taste seems to be little developed, but olfactory 
organs of considerable complexity are present in most 
forms, and consist of a pair of nostrils with olfactory 
papillae on their inner surfaces. The ears vary much in 
degree of organization, crocodiles and alligators being the 
only reptiles with a well-defined outer ear. This consists 
of a dermal flap covering a tympanum. Eyes are always 
present and are highly developed. They resemble the 
eyes of birds in many particulars. All reptiles, excepting 
the snakes and a few lizards, have movable eyelids, in- 
cluding a nictitating membrane like that of the birds. 
With the snakes the eye is protected by the outer skin, 
which remains intact over it, but is transparent and 
thickened to form a lens just over the inner eye. Turtles 
and lizards have a ring of bony plates surrounding the 



3 12 ELEMENTARY ZOOLOGY 

eyes similar to that of the birds. In addition to the usual 
eyes there is in many lizards a remarkable eye-like organ, 
the so-called pineal eye, which is situated in the roof of 
the cranium, and is believed to be the vestige of a true 
third eye, which in ancient reptiles was probably a well- 
developed organ. 

Life-history and habits. — Most reptiles lay eggs from 
which the young hatch after a longer or shorter period of 
incubation. Usually the eggs are simply dropped on the 
ground in suitable places (although certain turtles dig 
holes in which to deposit them), where they are incubated 
by the general warmth of the air and ground. However, 
some of the giant snakes, the pythons for instance, hold 
the eggs in the folds of the body. In the case of some 
snakes and lizards the eggs are retained in the body of 
the mother until the young hatch; such reptiles are said 
to be ovoviviparous, because the young, although born 
alive, are in reality enclosed in an egg until the moment 
of birth. Among reptiles the newly hatched young 
resemble the parents in most respects except in size, yet 
striking differences in coloration and pattern are not rare. 
But there is in this class no metamorphosis such as 
characterizes the post-embryonic development of the 
batrachians. 

The food of reptiles consists almost exclusively of 
animal substance, although some species, notably the 
green turtles and certain land-tortoises, are vegetable- 
feeders. The animal-feeders are mostly predaceous, the 
smaller species catching worms and insects, while the 
larger forms capture fishes, frogs, birds, and their eggs, 
small mammals, and other reptiles. 

Classification.— The living Reptilia are divided into 
four orders, of which one includes only a single genus, 
Hatteria, a peculiar lizard found in New Zealand. The 
other three are the Squamata, which includes the lizards 



BRANCH CHORD AT A: CLASS REP T I LI A 313 

and snakes,* distinguished by the scaly covering of the 
body, the Chelonia, which includes the tortoises and 
turtles, distinguished by the shell of bony plates which 
encloses the body, and the Crocodilia, which includes the 
crocodiles and alligators, whose bodies are covered with 
rows of sculptured bony scutes. 

Tortoises and turtles (Chelonia). — technical note.— 

Obtain specimens of some pond- or land-turtle common in the 
vicinity of the school. The red-bellied and yellow-bellied terrapins 
(Psendemys) or the painted or mud-turtles yClwysemys) are com- 
mon over most of the United States. [Pseudemys is found south of 
the Ohio River and Chrysemys north of it.) They may be raked 
up from creek-bottoms or fished for with strong hook and line, 
using meat as bait. They will live through the winter if kept in a 
cool place, without food or special care of any kind. Observe their 
swimming and diving, the retraction of head and limbs into the 
shell, the use of the third eyelid (nictitating membrane), and the 
swallowing of air. 

Examine the external structure of a dead specimen (kill by 
thrusting a bit of cotton soaked with chloroform or ether into the 
windpipe ; see opening just at base of tongue). Note shell consist- 
ing of a dorsal plate, the carapace, and ventral plate, the plastron, 
and the lateral uniting parts, the bridge. Note legs, and head with 
horny beak but no teeth. Compare with snake. The examination 
of the internal structure of the turtle can be readily made by saw- 
ing through the bridge on either side and removing the plastron. 
Note the ligaments which attach the plastron to the shoulder and 
pelvic girdles. Note muscles covering these bones. Note just 
behind the shoulder girdle the heart (perhaps still pulsating) and 
the dark liver on each side of it. Work out the alimentary canal, 
the trachea and lungs, and other principal organs, comparing them 
with those of the snake. The skeleton can be studied by dissecting 
and boiling and brushing away the flesh which still adheres to the 
bones. The comparison of the skeleton of the turtle with that of 
the snake is very instructive ; marked differences in the skeletons of 
the two kinds of reptiles are obviously correlated with the differ- 
ences in habits and shape of body. Note in the skeleton of the 
turtle especially the shoulder and pelvic girdles and limbs (absent in 
the snake) and small number of vertebrae and ribs. 

Among the common turtles and tortoises of the United 
States are several species of soft-shelled turtles (Trio- 

* By many zoologists the lizards and snakes are held to form two distinct 
orders, Lacertilia and Ophidia. 



314 ELEMENTARY ZOOLOGY 

nychidae) with carapace not completely ossified and both 
carapace and plastron covered by a thick leathery skin 
which is flexible at the margins ; the snapping-turtle 
(Chelydra sei'pentind), common in streams and ponds, with 
shell high in front and low behind and head and tail long 
and not capable of being withdrawn into the shell; the 
red-bellied and yellow-bellied terrapins (Pseudemys), red 
and yellow, with greenish-brow T n and black markings, 
common on the ground in woods and among rocks and 
also near water and sometimes in it; the pond- or mud- 
turtle (Chrysemys), also brightly colored and usually con- 
fined to ponds and pond-shores ; and the box-tortoise 
(Cistudo Carolina), common in woods and upland pastures 
and readily recognizable by its ability to enclose itself 
completely in its shell by the closing down of the lids 
of the plastron. All of these fresh-water and land-turtles 
except the soft-shelled turtles belong to one family, the 
Emydidae, but have somewhat diverse habits. Most of 
them are carnivorous, but few catch any very active 
prey. While some are strictly aquatic, others are as 
strictly terrestrial, never entering the water. The eggs 
of all are oblong and are deposited in hollows, sometimes 
covered in sand. The newly hatched young are usually 
circular in shape, and vary in color and pattern from the 
parents. 

The * ' diamond-back terrapin ' (Malaclemmys palus- 
tris), used for food, is a salt-water form " inhabiting the 
marshes along the Atlantic coast from Massachusetts to 
Texas. About Charleston [and Baltimore] they are 
very abundant and are captured in large numbers for 
market, especially at the breeding season, when the 
females are full of eggs. Further north they are dug 
from the salt mud early in their hibernation and are 
greatly esteemed, being fat and savory." 

Strongly contrasting with the usually small land- and 



BRANCH CHORD AT A: CLASS REPTILIA 



3 T 5 



fresh-water turtles are the great sea-turtles, such as the 
leather-back, the loggerhead and the green turtles. Some 
of these animals reach a length of six feet and more and 
a weight of nine hundred pounds, and have the feet com- 
pressed and fin-shaped for swimming. They live in the 
open ocean, coming on land only to lay their eggs, which 
are buried in the sand of ocean islands. These egg-laying 
visits are almost always made at night, and the turtles 




Fig. 124. — The giant land-tortoise of the Galapagos Islands, Testudo sp. 
These tortoises reach a length of four feet. (Photograph from life by 
Geo, Coleman.) 



are then often caught by "turtlers." The flesh of most 
of the sea-turtles is used for food, and from the shell of 
certain species, notably the " hawk-bill " {Eretmoclielys 
imbricatd) the beautiful "tortoise-shell " used for making 
combs and other articles is obtained. The common green 
turtle (CJielonia my das) of the Atlantic coast is the species 
most prized for food. It is a vegetarian, feeding on the 
roots of Zostera, the plant known in New England as 
eel-grass, though farther south it is called turtle-grass. 



3 l6 ELEMENTARY ZOOLOGY 

When grazing the turtles eat only the roots, the tops thus 
rising to the surface, where they indicate to the turtler the 
animal's whereabouts. The turtler, armed with a strong 
steel barb attached to a rope and loosely fitted to the end 
of a pole, carefully rows up to the unsuspecting animal, 
and with a strong thrust plunges the barb through its 
shell, withdraws the pole, and, grasping the rope, now 
firmly attached to the turtle's back, lifts the animal to the 
surface. Here, with assistance, he turns it into the boat, 
where it is rendered helpless by being thrown on its back 
and by having its flippers tied. These turtles are also 
caught on their breeding-gounds, being found on the sand 
at night by the turtler, turned over on their backs, and 
left thus securely caught until assistance comes to help 
get them into the boats. 

Snakes and lizards (Squamata). — Technical Note.— a 

snake has already been dissected and studied. It will be instructive 
to compare the external structures, at least, of a lizard with that o. 
the snake. Specimens of some species of the common swift (Scelo- 
porus) are obtainable almost anywhere in the United States. The 
" pine-lizards " of the east belong to this genus. Lizards may be 
sought for in woods, along fences, and especially on warm rocks. 




Fig. 125. — The blue-tailed skink, Eumeces skeltonianus. (From living 

specimen.) 

The group of lizards is a very large one, about 1,500 
species being known, but it is represented in the United 
States by comparatively few species. Lizards are espe- 
cially abundant in the tropics of South America. The 
strange and fantastic appearance presented by some of 
them has made certain species the object of much interest 



BRANCH CHORDA T A : CLASS REP T I LI A 3 l l 

and often fear on the part of the natives of tropical lands. 
In those regions are current extraordinary stories and 
beliefs regarding the habits and attributes of certain lizards 
like the basilisk and chameleon. Lizards are all more or 
less elongate and some are truly snake-like iri form. The 
legs, though usually present and functional, are in many 
cases much reduced, and in some forms, as the glass- 
snake, either one or both pairs are so rudimentary as to 
have no external projection whatever. Although lizards 



Fig. 126. — The Gila monster, Heloderma /wmdum, the only poisonous 
lizard. (Photograph from life by J. O. Snyder. 

are often regarded as being poisonous, only one genus, 
Heloderma, the Gila Monster, is really so. All others 
are perfectly harmless as far as poison is concerned, and 
most of them are unusually timid. They vary in size from 
a few inches to six feet in length. Most of them are ter- 
restrial, some arboreal, and some aquatic. 

Among the lizards of this country the swifts and ground- 
lizards are familiar everywhere. In certain regions the 
glass-snake or joint-snake {Opheosaurus v entrails) is 
common. This animal, popularly considered to be a 
snake, has no external limbs, and its tail is so brittle, the 
vertebrae composing it being very fragile, that part of it 
may break off at the slightest blow. In time a new tail 
is regenerated. It lives in the central and northern part 
of the United States, and burrows in dry places. In the 
western part of the country horned toads {Phrynosoma) 
are common, about ten different species being known. 
These are lizards with shortened and depressed body and 
well-developed legs. The body is covered with protec- 



3 t8 elementary zoology 

tive spiny protuberances, and in individual color and 
pattern resembles closely the soil, rocks, and cactus among 
which the particular horned toad lives. All the species 
of Plirynosoma are viviparous, seven or eight young being 
born alive at a time. 

In New Mexico, Arizona, and northern Mexico the only 
existing poisonous lizards, the Gila Monster (Helodenna) 
(fig. 126) is found. This is a heavy, deep-black, orange- 
mottled lizard about sixteen inches long. There is much 
variance of belief among people regarding the Gila Mon- 
ster, but recent experiments have proved the poisonous 
nature of the animal. The poison which is secreted by 
glands in the lower jaw flows along the grooved teeth into 
the wound. A beautiful and interesting little lizard found 
in the South is the green chameleon (Anolis principalis). 
Its body is about three inches long with a slender tail of 
five or six inches. The normal color of the chameleon is 
grass-green, but it may "assume almost instantly shades 
varying from a beautiful emerald to a dark and iridescent 
bronze color. ' 

In the tropics many of the lizards reach great size and 
are of strange shape and patterns. The flying dragons 
(Draco) have a sort of parachute on each side of the body 
composed of a fold of skin supported by five or six false 
posterior ribs. These lizards live in the trees of the East 
Indies and "fly " or sail from tree to tree. They are 
very beautifully colored. The iguanas (Iguana) of the 
tropics of South America are commonly used for food. 
They live mostly in trees, and reach a length of five or 
six feet. The monitor ( Varanus niloticus) is a great 
water-lizard that lives in the Nile, and feeds on crocodiles' 
eggs, of which it destroys great numbers. It is the prin- 
cipal enemy of the crocodile. When full grown it reaches 
a length of six feet or even more. 

About 1,000 living species of snakes are known.. 



BRANCH CHORD AT A : CLASS REP TI LI A 319 

Usually they have the body regularly cylindrical, and 
without distinct division into body regions. Legs are 
wanting, locomotion being effected by the help of the 
scales and the ribs. No snake can move forward on a 
perfectly smooth surface and no snake can leap. In some 
forms, such as the pythons, external rudiments of the hind 
limbs are present, but do not aid in locomotion. The 
mouth is large and distensible so that prey of considerably 
greater size than the normal diameter of the snake's body 
is frequently swallowed whole. The sense of taste is very 
little if at all developed, as the food is swallowed without 
mastication. The tongue, which is protrusible and usually 
red or blue-black, serves as a special organ of touch. 
Hearing is poor, the ears being very little developed. 
The sense of sight is also probably not at all keen. 
Snakes rely chiefly on the sense of smell for finding their 
prey and their mates. The colors of snakes are often 
brilliant, and in many cases serve to produce an effective 
protective resemblance by harmonizing with the usual 
surroundings of the animal. The food of snakes consists 
almost exclusively of other animals, which are caught 
alive. Some of the poisonous snakes kill their prey before 
swallowing it, as do some of the constrictors. While most 
snakes live on the ground, some are semi-arboreal and 
others spend part or all of their time in water. Cold- 
region snakes spend the winter in a state of suspended 
animation ; in the tropics, on the contrary, the hottest part 
of the year is spent by some species in a similar 4t sleep. " 
There are so many common snakes in the United States 
that only a few of the more familiar forms can be men- 
tioned. The non-poisonous species of America belong 
to the family Colubridae, while all but one of the poisonous 
species belong to the family Crotalidre, characterized by 
the presence of a pair of erectile poison-fangs on the upper 
jaw. Among the commonest of the Colubridae are the 



3 2 ° 



ELEMENTARY ZOOLOGY 



garter snakes {Thamnophis) (fig. 127), always striped and 
not more than three feet long. The most widespread 
species is Thamnophis sirtalis, rather dully colored with 
three series of small dark spots along each side. The 




Fig. 127. — A garter snake, Thamnophis parietalis. (Photograph from life 

by J. O. Snyder.) 

common water-snake {Natrix sipedori) is brownish with 
back and sides each with a series of about 80 large square 
dark blotches alternating with each other. It feeds on 
fishes and frogs, and although " unpleasant and ill-tem- 
pered " is harmless. One of the prettiest and most gentle 
of snakes is the familiar little greensnake {Cyclopias 
cestivus), common in the East and South in moist 
meadows and in bushes near the water. It feeds on in- 
sects and can be easily kept alive in confinement. A 
familiar larger snake is the blacksnake or blue racer {Bas- 
caniom constrictor), "lustrous pitch black, general color 
greenish below and with white throat. ' : It is "often 
found in the neighborhood of water, and is particularly 
partial to thickets of alders, where it can hunt for toads, 
mice, and birds, and being an excellent climber it is often 
seen among the branches of small trees and bushes, 
hunting for young birds in the nest.' The chain-snake 
{Lampropeltis getulus) of the southeast and the king- 
snake (also a Lampropeltis) (fig. 128) of the central 



BRANCH CHORD AT A: CLASS RE PT I LI A 



12 1 



States are beautiful lustrous black-and-yellow spotted 
snakes which feed not only on lizards, salamanders, 
small birds and mice but also on other snakes. The 
king-snake should be protected in regions infested by 
1 ' rattlers. ' : The spreading adder or blowing viper 
(JHcterodon platirhiiws), a common snake in the eastern 
States, brownish or reddish with dark dorsal and lateral 
blotches, depresses and expands the head when angry, 
hissing and threatening. Despite the popular belief in its 
poisonous nature this ugly reptile is quite harmless. It 
specially infests dry sandy places. 

With the exception of the coral or beadsnake (Elaps 
fulvius), a rather small jet-black snake with seventeen 
broad yellow-bordered crimson rings, found in the 
southern States, the only poisonous snakes of the United 
States are the rattlesnakes and their immediate relatives, 
the copperhead and water-moccasin. These snakes all 
have a large triangular head, and the posterior tip of the 
body is, in the rattlesnakes, provided with a "rattle" 




Fig. 128. — A king-snake, Lampropeltis boy Hi, (Photograph from life by 

J. O. Snyder.) 

composed of a series of partly overlapping thin horny 
capsules or cones of shape as shown in figure 130. These 
horny pieces are simply the somewhat modified succes- 
sively formed epidermal coverings of the tip of the body. 



322 ELEMENTARY ZOOLOGY 

which instead of being entirely molted as the rest of the 
skin is, are, because of their peculiar shape, loosely attached 
to one another, and by the basal one to the body of the 
snake. The number of rattles does not correspond to the 
snake's years for several reasons, partly because more 
than one rattle can be added to the tail in a year, and 
especially because rattles are easily and often broken off. 
As many as thirty rattles have been found on one snake. 
There are two species of ground-rattlesnakes or massa- 



FlG. 129. The gopher-snake. Pituophis bellona. (Photograph from life 

by J. O. Snyder.) 



saugas {Sistriiriis) in the United States and ten species of 
the true rattlesnakes {Crotalus). The centre of distribu- 
tion of the rattlesnakes is the dry tablelands of the south- 
west in New Mexico, Arizona, and Texas. But there are 
few localities in the United States outside the high moun- 
tains in which "rattlers " do not occur or did not occur 
before they were exterminated by man. The copperhead 
(Agkistrodon contortix) is light chestnut in color, with 
inverted Y-shaped darker blotches on the sides, and 



BRANCH CHORD AT A: CLASS REFT ILIA 



3 2 



seldom exceeds three feet in length. It occurs in the 
eastern and middle United States from Pennsylvania and 
Nebraska southward. It is a vicious and dangerous 
snake, striking without warning. The water-moccasin 
[Agkistrodon piscivorous) is dark chestnut-brown with 
darker markings. The head is purplish black above. 
It is found along the Atlantic and Gulf coasts from North 
Carolina to Mexico, extending also some distance up the 
Mississippi valley. It is distinctively a water-snake, being 
found in damp swampy places or actually in water. It 
reaches a length of over four feet and is a very venomous 
snake, striking on the slightest provocation. The com- 
mon harmless water-snake is often called water-moccasin 
in the southern States, being popularly confounded with 
this most dangerous of our serpents. The poison of all of 
these snakes is a rather yellowish, transparent, sticky fluid 
secreted by glands in the head, from which it flows through 





Fig, 130. — The rattles of the rattlesnake; the lower figure shows a longi^ 
tudinal section of the rattle. 



the hollow maxillary fangs. The character and position 
of the fangs are shown in figure 131. Remedial measures 
for the bite of poisonous snakes are, first, to stop, if possi- 
ble, the flow of blood from the wound to the heart, by 



324 ELEMENTARY ZOOLOGY 

compressing the veins between the wound and heart, then 
to suck (if the lips are unbroken) the poison from the 
wound, next to introduce by hypodermic injection per- 
manganate of potash, bichloride of mercury or chromic 
acid into the wound, and finally perhaps to take some 
strong stimulant as brandy or whiskey. 

Of the kinds of snakes not found in this country perhaps 
the most interesting are the gigantic boa constrictors, 
anacondas, and pythons. Pythons are found in India, 
the islands of the Malay archipelago, and Australia, while 
the boas and anacondas live in the tropics of America. 
The largest pythons reach a length of thirty feet and some 
of the boas are nearly as large. These snakes feed on 




Fig. 131. — Dissection of head of rattlesnake; /, poison-fangs; /, poison-sac. 

small mammals such as fawns, kids, water-rats, etc., and 
birds. The prey is swallowed whole, being first encircled 
and crushed to death in folds of the body. After a meal 
the python or boa lies in a sort of torpor for some time. 
A famous snake is the deadly cobra-da-capello of India. 
These snakes are so abundant and the bite is so nearly 
certainly fatal that thousands of persons are killed each 
year in India by it. Other extremely poisonous snakes 
are the vipers ( Vipera cerastes), which live in the hot 
deserts of northern Africa. Over each eye there is a scaly 



BRANCH CHORD AT A: CLASS REPTJUA 3 2 5 

spine or horn, from which the name horned viper is 
derived. The most poisonous snake of South Africa is 
the large and ugly puff-adder, which puffs itself up when 
irritated. An interesting group of snakes is that of the 
Hydrophidae or sea-snakes, which swim on the surface of 
the ocean by means of their flattened and oar-like tails. 
These forms live in the tropical portions of the Indian and 
Pacific oceans, ranging as far north as the Gulf of Cali- 
fornia, and spend their whole life in the water, "out of 
which they appear to be blind and soon die. ,: They are 
extremely venomous, but are all of small size, rarely two 
feet long. 

Crocodiles and alligators (Crocodilia). — The crocodiles 
and alligators are reptiles familiar by name and appear- 
ance, though seen in nature only by inhabitants or visitors 
in tropical and semitropical lands. In the United States 
there are two species of these great reptiles, the American 
crocodile (Crocodilus americamis), living in the West 
Indies and South America and occasionally found in 
Florida, and the American alligator {Alligator missis- 
sippiensis), common in the morasses and stagnant pools 
of the southern States. The alligator differs from the 
crocodiles in having a broader snout. It is rarely more 
than twelve feet long. The best-known crocodile is the 
Nile crocodile, which is not limited to the Nile, but is 
found throughout Africa. In the Ganges of India is 
found another member of this group of reptiles called the 
gavial. It is among the largest of the order, reaching a 
length of twenty feet. The crocodiles, alligators, and 
gavials comprise not more than a score of species 
altogether, but because of their wide distribution, great 
size, and carnivorous habits they are among the most 
conspicuous of the larger living animals. They live mostly 
in the water, going on land to sun themselves or to lay 
their eggs. They move very quickly and swiftly in water 



326 ELEMENTARY ZOOLOGY 

but are awkward on land. Fish, aquatic mammals and 
other animals which occasionally visit the water are their 
prey. The gavial and Nile crocodile are both known to 
attack and devour human beings, and these species 
annually cause a considerable loss of life. But few such 
fatalities, however, are accredited to the American alli- 
gator. 



CHAPTER XXVII 

BRANCH CHORDATA {Continued). CLASS AVES: 

THE BIRDS 

THE ENGLISH SPARROW (Passer domesticus) 

Technical Note. — The English sparrow may be found now in 
cities and villages all over the United States. It has become a 
veritable pest, and the killing of the few needed for the laboratory 
may be looked on as desirable rather than deplorable, as is the 
killing of birds in almost all other cases. The males have a black 
throat, with the other head-markings strong and contrasting (black, 
brown, and white), while the females have a uniform grayish and 
brownish coloration on the head. 

Specimens are best taken alive, as shooting usually injures them 
for dissection. One can rely on the ingenuity of the boys of the 
class to procure a sufficient number of specimens. Observations 
on the habits of the birds should be made by the pupils as they go 
to and from school. For dissection use fresh specimens if possible. 
If desirable a pigeon or dove may be used in place of the sparrow. 

External structure. — Note in the sparrow the same 
general arrangement of body parts as in the toad, the 
body being divided into head, tipper limbs, trunk, and 
lower limbs. In the toad, however, all of the limbs are 
fitted for walking and jumping, whereas in the sparrow the 
anterior pair of appendages, the wings, are modified to 
be organs of flight, and the posterior limbs are specially 
adapted for perching. Note that the sparrow is covered 
with feathers, some long, some short, in some places thick 
and in others thin, but all fitting together to form a com- 
plete covering for the body. Note also that the anterior 

end of the head is prolonged into a hard bony structure, 

327 



32S ELEMENTARY ZOOLOGY 

the bill, covered with horny substance. This horny sub- 
stance together with the feathers and horny covering of 
the feet are modified portions of the skin. Note the long 
quill-feathers attached to the posterior edge of the wing. 
By these the bird sustains its flight. Other long quill- 
feathers are attached to the posterior end of the body, 
forming the tail. By a system of muscles connected with 
these feathers they act together, serving as a rudder during 
flight and as a balancing contrivance when perching. 
Note just above the bill two openings protected by tufts 
of feathers. What are these openings ? How are they 
connected with the month ? Note the large eyes, and at 
the inner angle of each the delicate nictitating membrane 
which can be drawn over the ball. Does the bird have 
external ears ? Lift the feathers just above the tail (the 
upper tail-coverts) and note a small median gland, the 
oil-gland, from which the bird derives the oil with which 
it oils its feathers. Beneath the tail note the opening 
from the alimentary canal and from the kidneys and 
reproductive organs. This is called the cloacal opening. 

Examine in detail some of the feathers. In one of the 
quill-feathers note the central stem or shaft composed of 
two parts, a basal hollow quill, which bears no web and 
by which the feather is inserted in the skin, and a longer, 
terminal, four-sided portion, the rachis, which bears on 
either side a web or vane. Each vane is composed of 
many narrow linear plates, the barbs, from which rise 
(like miniature vanes) many barbules. Each barbule 
bears many fine barbicels and hamnli or hooklets. The 
barbs of the feather are interlocked. How is this effected ? 
The feathers which overlie the whole body and bear the 
color pattern are called contour-feathers. How do they 
differ from or correspond with the quill-feathers in struc- 
ture ? Soft feathers called dozvn-f eat hers, or plumiries, 
cover the body more or less completely, being, however, 



BRANCH CHORD AT A; CLASS AVBS : THE BIRDS 329 

mostly hidden by the contour-feathers ; the barbs of these 
are sometimes not borne on a rachis, but arise as a tuft 
from the end of the quill. Certain other feathers which 
have an extremely slender stem and usually no vane, 
except a small terminal tuft of barbs, are called tJiread- 
featliers, or filo plumules. They are rather long, but are 
mostly hidden by the contour-feathers. In certain birds 
they stand out conspicuously, as the vibrissa about the 
nostrils. 

In the determination of birds by the use of a classifica- 
tory "key' (see p. 359 it is necessary to be familiar 
with the names applied to the various external regions of 
the body and plumage, and with the terms used to denote 
the special varying conditions of these parts. By refer- 
ence to figure 133 the names of the regions or parts most 
commonly referred to may be learned. A full account 
of all of the external characters with definitions of the 
various terms used in referring to them may be found in 
Coues's " Key to North American Birds." 

Technical Note.— -Pull the feathers from the body, being care- 
ful not to tear the skin. 

In the fish and toad, already studied, the head is closely 
joined to the trunk. How is it with the bird ? Observe 
that the knee of the sparrow is covered by feathers and 
that it is the ankle which extends down as the bare un- 
feathered part to the digits. How many digits have the 
feet of the bird ? How are they arranged ? 

Internal structure (fig. 132). — technical Note.— with a 

pair of scissors cut just beneath the skin anteriorly from the cloacal 
opening to the angle of the lower jaw. Pin the sparrow on its back 
by the wings, feet, and bill. Push back the skin from both sides 
and pin out. 

Note the large powerful pectoral muscles. Note a hard 
median projection of bone, the sternum, which is a large 



33° 



ELEMENTARY ZOOLOGY 




BRANCH CHORD AT A; CLASS AVES : THE BIRDS 331 

keel-shaped bone with lateral expansions to which are 
attached the ribs. Where are the largest and most 
powerful muscles of the toad located ? Where are they 
in the fish ? In the bird the most powerful muscles are 
these pectoral muscles, which move the wings in flight. 

Technical Note. — Cut the pectoral muscles from the left side 
of the sternum, push back and pin to one side. With a strong pair 
of scissors cut through the ribs on the left side of the sternum and 
through the overlying bones. Lift the whole sternum, with the 
right pectoral muscle attached, to the left side of the pan and pin it 
down. Cut through the membrane which covers the viscera and 
cover the dissection with water. 

In this operation note the V-shaped wishbone in front 
of the sternum. It is composed of the two clavicles with 
their inner ends fused. Note the stout coracoid bones 
extending from the anterior end of the sternum to the 
shoulder. 

Note near the middle of the body the Jieart with the 
large blood-vessels proceeding from it. Behind the heart 
lies the large reddish-brown liver, and on the left side 
below the liver is the large gizzard or muscular stomach. 
Note the viscera folded over themselves in the body- 
cavity. Push them temporarily aside and note in the 
dorsal region under the heart large pinkish spongy sacs, 
the lungs. These are attached by short tubes, the 
bronchi, to the long cartilaginous trachea. At the union 
of the bronchi with the trachea is a small expansion with 
cartilaginous walls, within which are stretched small bands 
of muscles. This organ is the syrinx, the song- or voice- 
apparatus of the bird. It should be cut open and carefully 
examined. Trace the trachea forward to its anterior end. 
It opens by a glottis into the larynx, a slightly swollen 
chamber with cartilaginous walls. Note the U-shaped 
hyoid bone surrounding the front of the glottis. Through 
a blowpipe or quill inserted into the glottis blow air into 
the trachea and observe the inflation of the lungs and of 



33 2 ELEMENTARY ZOOLOGY 

certain large air-sacs in the abdomen, which communicate 
with them. 

Beneath the trachea note the long oesophagus. Inflate 
the oesophagus with a blowpipe and note how distensible 
is its lower end near the breast. This distensible portion 
is called the crop. If the alimentary canal be drawn out 
straight the oesophagus will be found to run as an almost 
straight tube down the left side of the body to the gizzard. 
This latter organ has very thick muscular walls and in it 
the food is ground up among the small bits of gravel it 
contains. Extending from the gizzard near the entrance 
of the oesophagus note the long pyloric loop of the intes- 
tine called duodenum. Within this loop is a long pinkish 
gland, the pancreas, which empties by a duct into the 
duodenum. Into the duodenum also the overlying liver 
empties its secretion of bile from the median-placed gall- 
bladder. From the duodenum the small intestine or ileum 
extends with many convolutions to its exit through the 
cloacal aperture. On the intestine near the cloacal open- 
ing note a pair of glandular structures, the cceca. The 
short part of intestine between the caeca and cloaca is 
called the rectum. On the left side of the body beneath 
the gizzard note a dark glandular structure, the spleen. 

Make a drawing of the dissection as so far worked out. 

Technical Note — Remove the alimentary canal, cutting it free 
posteriorly at the caeca and anteriorly just above the muscular gizzard. 
Cut open the gizzard and note its structure. The contained sand 
and gravel grains are picked up by the bird as it eats. 

On either side of the throat note the well-defined thyroid 
gland ; in young sparrows will be noted on each side cf 
the neck a mass of tissue, the remains of the thymus 
gland, which disappears in the adult. 

Cut transversely through the lower end of the heart and 
note that the ventricles are wholly distinct, whereas in the 
toad and snake they are incompletely separated In the 



BRANCH CHORD AT A; CLASS AVES : THE BIRDS 333 

bird there is a complete double circulation. Its blood is 
not mixed, the pure with the impure, as in the toad and 
snake. Blood passing through the right auricle and ven- 
tricle goes to the lungs; on its return to the heart purified, 
it enters the left auricle and left ventricle, thence to pass 
out over the body through the arteries. 

Note the large aorta given off from the left ventricle. 
Note the two large branches, the innominate arteries, 
given off by it near its origin. Each innominate divides 
into three smaller arteries, a carotid, branchial, and pec- 
toral. The aorta itself turns toward the back and con- 
tinues posteriorly through the body as the dorsal aorta. 
To the right auricle come three large veins, the right and 
left pra?cavce and the postcava. Each praecava is formed 
by three veins, the jugular from the head, the brancliial 
from the wing, and the pectoral from the pectoral muscles. 
The postcava comes from the liver. From the right 
ventricle go the short right and left pulmonary arteries 
to the lungs, and from the lungs the blood is brought to 
the left auricle through the right and left pidmonary veins. 

Technical Note. — For a detailed study of the circulation of 
the bird the teacher should inject the blood system of some larger 
bird, as a pigeon or fowl, for a class-demonstration. (For a guide, 
use Parker's "Zootomy," p. 209, or Martin and Moale's " How to 
Dissect a Bird," pp. 1 35-140 and pp. 148, 149.) 

In the posterior dorsal region of the body-cavity will 
be found large three-lobed organs fitting into the spaces be- 
tween the bones of the back on either side. These are the 
kidneys, and from their outer margins on each side a ureter 
runs posteriorly into the cloaca. Overlying the anterior 
ends of the kidneys are the reproductive organs. In the 
male these glands consist of firm, whitish, glandular 
bodies. From each runs a long convoluted vas deferens, 
which enters the cloaca. This tube corresponds to the 
egg-duct of the female. In the female the rig lit egg- 



334 ELEMENTARY ZOOLOGY 

g land and egg-duct or oviduct are wanting. The left egg- 
gland appears as a glandular mass; during the breeding] 
season yellow ova or eggs in various stages of develop- 
ment project from its surface. The oviduct opens by al 
funnel-shaped mouth near the egg-gland and runs thence 
to the cloaca. The eggs pass from the egg-gland into the 
body-cavity, where they are caught in the upper end of 1 
the oviduct and carried down and out through the cloacal 
opening. It is in the oviduct that the egg derives its 
accessory covering, which consists of a white or albumin- 
ous portion, together with several enveloping membranes 
and the hard shell enclosing all. 

Remove the top of the skull and note the large brain. 
What portions of the brain make up the greater part of 
it ? Note the differences between this brain and that of 
the toad. Trace the principal cranial nerves. Work out 
the spinal cord and principal spinal nerves. For an 
account of the nervous system of the sparrow see Martin 
and Moale's "How to Dissect a Bird," pp. 150-163. 

Technical Note. — For a study of the skeleton of the sparrow 
a specimen should be cleaned by boiling in a soap-solution (see p. 

452). 

In the sparrow's skeleton note the compactness of the 
skull and the fusion of its bones. Observe the long 
cervical vertebrce w T hich support the skull, also the 
thoracic vertebrce bearing the ribs and sternum. How 
many of each of these kinds of vertebrae are there ? The 
vertebrae posterior to the thorax are more or less fused 
together to form the sacrum, which, with the pelvic girdle, 
supports the leg-bones. The bones of the tail consist of 
a number of very small vertebrae, some of which are fused 
together. Note the correspondence between the bones 
of the leg and those of the wing. What are the names 
of each of the bones of each limb, and what are the corre- 
sponding bones in the two limbs ? The wings and legs 







OS 




&. 






s 

s 




<3 




&» 


••^ 


o 






C3 


g 






S3 




o 






no 


<^> 








8 


a- 


\ 




$3 


cs 


x^ 


x j 




£ 


1 




^<i 





5* 

I 








Is 



g 

a 

Cm 
in 















BRANCH CHORD AT A; CLASS AVES : THE BIRDS 335 

being modified for different uses, their various bones have 
assumed different relations to each other and to the body, 
for they are bent at directly opposite angles and the 
attachment of muscles is different. Compare the skeleton 
of the bird with that of the toad, (For a detailed account 
of the skeleton of the bird see Parker's ''Zootomy,' 
pp. 182—209, or Martin and Moale's " How to Dissect a 
Bird," pp. 102-125.) 

Life-history and habits. — The English sparrow was 
first introduced into the United States in 1850, and since 
that time has rapidly populated most of the cities and 
towns of the country. On account of its extreme adapt- 
ability to surroundings, its omnivorous food-habits and its 
fecundity it survives where other birds would die out. 
It also crowds out and has caused the disappearance or 
death of other birds more attractive and more useful. 
The sparrow annually rears five or six broods of young, 
laying from six to ten eggs at each sitting. Had it no 
enemies a single pair of sparrows would multiply to a 
most astonishing number. The sparrow has, however, a 
number of enemies, most common among them perhaps 
being the " small boy," but birds and mammals play the 
chief part in the destruction. The smaller hawks prey 
upon them, and rats and mice destroy great numbers of 
their young and of their eggs whenever the nests can be 
reached. The sparrow is omnivorous and when driven 
to it is a loathsome scavenger, though at other times its 
tastes are for dainty fruits. Its senses of perception are 
of the keenest; it can determine friend or foe at long 
range. The nesting habits are simple, the nests being 
roughly made of any sort of twigs and stems mixed with 
hair and feathers and placed in cornices or trees. A 
maple-tree in a small Missouri town contained at one time 
thirty-seven of these nests. 



336 ELEMENTARY ZOOLOGY 

OTHER BIRDS. 

Birds are readily and unmistakably distinguishable from 
all other kinds of animals by their feathers. They are 
further distinguished from the reptiles on one hand by 
their possession of a complete double circulation and by 
their warm blood (normally of a temperature of from 
100-112 F.), and from the mammals on the other by 
the absence of milk-glands. There are about 10,000 
known species of living birds ; they occur in all countries, 
being most numerous and varied in the tropics. Birds 
are exceptionally available animals for the special atten- 
tion of beginning students, because of their abundance and 
conspicuousness and the readiness with which their varied 
and interesting habits may be observed. The bright 
colors and characteristic manners which make the identifi- 
cation of the different kinds easy, the songs and flight, 
and the feeding, nesting and general domestic habits of 
birds are all excellent subjects for personal field-studies 
by the students. We shall therefore devote more atten- 
tion to the birds than to the other classes of vertebrates, 
just as we selected the insects among the invertebrates for 
special consideration. 

Body form and structure. — The general body form 
and external appearance of a bird are too familiar to need 
description. The covering of feathers, the modification 
of the fore limbs into wings, and the toothless, beaked 
mouth are characteristic and distinguishing external 
features. The feathers, although covering the whole of 
the surface of the body, are not uniformly distributed, but 
are grouped in tracts called pterylce, separated by bare or 
downy spaces called apteria. They are of several kinds, 
the short soft plumules or down-feathers, the large stiffer 
contour-feathers, whose ends form the outermost covering 
of the body, the quill-feathers of the wings and tail, and 



BRANCH CHORD AT A ; CLASS AVES : THE BIRDS 337 

the fine bristles or vibrissas about the eyes and nostrils 
called thread-feathers. The fore limbs are modified to 
serve as wings, which are well developed in almost all 
birds. However, the strange Kiwi or Apteryx of New 
Zealand with hair-like feathers is almost wingless, and the 
penguins have the wings so reduced as to be incapable of 
flight, but serving as flippers to aid in swimming under- 
neath the water. The ostriches and cassowaries also 
have only rudimentary wings and are not able to fly. 
Legs are present and functional in all birds, varying in 
relative length, shape of feet, etc., to suit the special 
perching, running, wading, or swimming habits of the 
various kinds. Living birds are toothless, although 
certain extinct forms, known through fossils, had large 
teeth set in sockets on both jaws. The place of teeth is 
taken, as far as may be, by the bill or beak formed of the 
two jaws, projecting forward and tapering more or less 
abruptly to a point. In most birds the jaws or mandibles 
are covered by a horny sheath. In some water and shore 
forms the mandibular covering is soft and leathery. The 
range in size of birds is indicated by comparing a humming- 
bird with an ostrich. 

Many of the bones of birds are hollow and contain air. 
The air-spaces in them connect with air-sacs in the body, 
which connect in turn with the lungs. Thus a bird's 
body contains a large amount of air, a condition helpful 
of course in flight. The breast-bone is usually provided 
with a marked ridge or keel for the attachment of the 
large and powerful muscles that move the wings, but in 
those birds like the ostriches, which do not fly and have 
only rudimentary wings, this keel is greatly reduced or 
wholly wanting. The fore limbs or wings are terminated 
by three ''fingers' only; the legs have usually four, 
although a few birds have only three toes and the ostriches 
but two. 



33 s ELEMENTARY ZOOLOGY 

As birds have no teeth with which to masticate their 
food, a special region of the alimentary canal, the gizzard, 
is provided with strong muscles and a hard and rough 
inner surface by means of which the food is crushed. 
Seed-eating birds have the gizzard especially well devel- 
oped, and some birds take small stones into the gizzard 
to assist in the grinding. The lungs of birds are more 
complex than those of batrachians and reptiles, being 
divided into small spaces by numerous membranous par- 
titions. They are not lobed as in mammals, and do not 
lie free in the body-cavity, but are fixed to the inner dorsal 
region of the body. Connected with the lungs are the 
air-sacs already referred to, which are in turn connected 
with the air-spaces in the hollow bones. By this arrange- 
ment the bird can fill with air not only its lungs but all 
the special air-sacs and spaces and thus greatly lower its 
specific gravity. The vocal utterances of birds are pro- 
duced by the vocal cords of the syrinx or lower larynx, 
situated at the lower end of the trachea just where it 
divides into the two bronchial tubes, the tracheal rings 
being here modified so as to produce a voice-box con- 
taining two vocal cords controlled by five or six pairs 
of muscles. The air passing through the voice-box strikes, 
against the vocal cords, the tension of which can be varied 
by the muscles. In mammals the voice-organ is at the 
upper or throat end of the trachea. 

The heart of birds is composed of four distinct cham- 
bers, the septum between the two ventricles, incomplete 
in the Reptilia, being in this group complete. There is 
thus no mixing of arterial and venous blood in the heart. 
The systemic blood-circulation being completely separated 
from the pulmonic, the circulation is said to be double. 
The circulation of birds is active and intense ; they have 
the hottest blood and the quickest pulse of all animals. 
In them the brain is compact and large, and more highly 



BRANCH CHORD AT A; CLASS AVES : THE BIRDS 339 

developed than in batrachians and reptiles, but the cere- 
brum has no convolutions as in the mammals. Of the 
special senses the organs of touch and taste are apparently 
not keen; those of smell, hearing, and sight are well 
developed. The optic lobes of the brain are of great size, 
relatively, compared with those of other vertebrate brains, 
and there is no doubt that the sight of birds is keen and 
effective. The power of accommodation or of quickly 
changing the focus of the eye is highly perfected. The 
structure of the ear is comparatively simple, there being 
ordinarily no external ear, other than a simple opening. 
The organs of the inner ear, however, are well developed, 
and birds undoubtedly have excellent hearing. The 
nostrils open upon the beak, and the nasal chambers are 
not at all complex, the smelling surface being not very 
extensive. It is probable that the sense of smell is not, 
as a rule, especially keen. 

Development and life-history. — All birds are hatched 
from eggs, which undergo a longer or shorter period of 
incubation outside the body of the mother, and which are, 
in most cases, laid in a nest and incubated by the parents. 
The eggs are fertilized within the body of the female, the 
mating time of most birds being in the spring or early 
summer. Some kinds, the English sparrow, for example, 
rear numerous broods each year, but most species have 
only one or at most two. The eggs vary greatly in size 
and color-markings, and in number from one, as with 
many of the Arctic ocean birds, to six or ten, as with most 
of the familiar song-birds, or from ten to twenty, as with 
some of the pheasants and grouse. The duration of in- 
cubation (outside the body) varies from ten to thirty days 
among the more familiar birds, to nearly fifty among the 
ostriches. The temperature necessary for incubation is 
about 40 C. (ioo° F.). Among polygamous birds 
(species in which a male mates with several or many 



34o 



ELEMENTARY ZOOLOGY 



females) the males take no part in the incubation and little 
or none in the care of the hatched young; among most 
monogamous birds, however, the male helps to build the 
nest, takes his turn at sitting on the eggs, and is active in 
bringing food for the young, and in defending them from 
enemies. The young, when ready to hatch, break the 
egg-shell with the " egg-tooth, a horny pointed projec- 
tion on the upper mandible, and emerge either blind and 




Fig. 134. — The nest and eggs of the black phcebe, Sayomis nigricans. 
(Photograph by J. O. Snyder.) 



almost naked, dependent upon the parents for food until 
able to fly (altricial young), or with eyes open and with 
body covered with down, and able in a few hours to feed 
themselves (precocial young). 

More details regarding the eggs, nest, and young of 
birds will be given later in this chapter. 

Classification. — The class Aves is usually divided into 
numerous orders, the number and limits of these as pub- 
lished in zoological manuals varying according to the 



BRANCH CHORD AT A; CLASS AVES : THE BIRDS 34 I 

opinions of various zoologists. The rank of an order in 
this group is far lower than in most other classes. In 
other words, the orders are very much alike and are 
recognized mainly for the convenience in breaking up the 
vast assemblage of species. In North America practically 
all the ornithologists have agreed upon a scheme of 
classification, which will therefore be adopted in this book. 
According to this classification the eight hundred (approxi- 
mately) known species of North American birds represent 
seventeen orders. Certain recognized orders, for example, 
the ostriches, are not represented naturally in North 
America at all. As birds can usually be readily identi- 
fied, the species being easily distinguished by general 
external appearance, and as there are many excellent 
book-guides to their classification, the beginning student 
can specially well begin with them his study of systematic 
zoology, which concerns the identification and classifica- 
tion of species. In a later paragraph are given therefore 
some suggestions for field and laboratory work in the 
determination of local bird-faunse. In the following para- 
graphs each of the American orders is briefly discu cc ^d, as 
is also the foreign order of ostriches. 

The ostriches, cassowaries, etc. (Ratitae). — The os- 
triches, familiar to all from pictures and to some from 
live individuals in zoological gardens and menageries, 
or stuffed specimens in museums, together with a few 
other similar large species, are distinguished from all 
other birds by having the breast-bone flat instead of 
keeled. There are about a score of species of ostriches 
and ostrich-like birds all confined to the southern hemi- 
sphere. In them the wings are so reduced that flight is 
impossible, but the legs are long and strong, and they can 
run as swiftly as a galloping horse. They are said to have 
a stride of over twenty teet. They use their legs also as 
weapons, kicking viciously when angered. The true 



342 



ELEMENTARY ZOOLOGY 



ostriches {Struthio camelus) (fig. 135) live in Africa. They 
are the largest living birds, reaching a height of nearly 
seven feet and weighing as much as two hundred pounds. 
They are hunted for their feathers, and are now kept in 
captivity and bred in South Africa and California for 
the same purpose. About five million dollars' worth of 




Fig. 135. — Ostriches on ostrich farm at Pasadena, California. (Photo- 
graph from life.) 

ostrich-feathers are used each year. The eggs, which are 
from five to six inches long and nearly five inches thick, 
are laid in shallow hollows scooped out in the sand of the 
desert. The male undertakes most of the incubation, 
although when the sun is hot no brooding is necessary. 



BRANCH CHORDATA; CLASS AVES : THE BIRDS 343 

The young (fig. 136) hatch in from seven to eight weeks, 
and can run about immediately. 

The rheas, found in South America, and the cassowaries 
of Australia are the only other living ostrich-like birds. 




Fig. 136. — Young ostriches just from egg: on ostrich farm at Pasadena. 
California. (Photograph from life.) 

Their feathers are of much less value than those of the 
true ostrich. 

The loons, grebes, auks, etc. (Pygopodes). — The 

loons, grebes, and auks are aquatic birds, living in both 
ocean and fresh waters. Their feet are webbed or lobed, 
and their legs set so far back that walking is very difficult 
and awkward. But all the birds of this order are excel- 
lent swimmers and divers. They are distinctively the 
diving birds. They have short wings and almost no tail. 
The dab-chick or pied-billed grebe {Podilymbus podiccps) 
is common in ponds over all the country. Its eggs are 
laid in a floating nest of pond vegetation and are often 
covered with decaying plants. The horned grebe 
(Colymbus auritus) is common west of the Mississippi in 
lakes and ponds. The loon or great northern diver 



344 



ELEMENTARY ZOOLOGY 













IHssr^ "v % 


, 


ifci 


MS? 


f 






[."■■■ 


P r - *.i-% 






IP * * Us- ^B". 






|i L^ '^^^fc 


'* 


Hp ~^wf ^ 




I; 




mHk 


W : 


: - '<*."-' :,3 ' : : ' : "*" '| 


. 


[; 


"" ■ * '■ . . ,;.,.,, ■ 




■*"fi; .' 


■^■ : ' 








,v 








■ ; ' r ' ; ,r, , ™^ 



BRANCH CHORD AT A; CLASS AVBS : THE BIRDS 345 

(Gavia imber), found all over the United States in winter, 
is the largest of this group, reaching a length (from bill to 
tip of tail) of three feet. It is black above with many 
small white spots, and with a patch of white streaks on 
each side of the neck and on the throat ; it is white on 
breast and belly. The female is duller, being brownish 
instead of black. 

The auks, guillemots, puffins, and murres (fig. 137) 
are ocean birds which gather, in the breeding season, in 
countless numbers on the bleak rocks and inaccessible 
cliffs of the northern oceans. Each female lays a single 
egg (in some cases two or at most three) on the bare rock 
or in a crevice or sort of burrow. These birds mostly fly 
well, but are especially at home in the water, feeding ex- 
clusively on animal substances found there. A famous 
species is the great auk (A lea impennis), which has 
become extinct in historical times. The last living speci- 
men was seen in 1844. 

The gulls, terns, petrels, and albatrosses (Longi- 
pennes).— The Longipennes are water-birds, mostly 
maritime, with webbed feet and very long and pointed 
wings. They are all strong flyers, and most of them 
are beautiful birds. Their prevailing colors are white, 
slaty or lead-blue, black, and, in the young, mottled 
brownish. They subsist chiefly on fish, but an}' animal 
substance will be eagerly picked up from the water; some 
of the gulls forage inland. Occasionally great flocks may 
be seen following a plow near the shore and feeding on 
the grubs and worms exposed in the freshly-turned soil. 
Some of the gulls, like the great black-backed gull (Larus 
marinus), attain a length of two and one-half feet. The 
terns {Sterna) are mostly smaller than the gulls, have a 
bill not so heavy and not hooked, and have the tail 
forked. 

The fulmars, shearwaters, petrels, and albatrosses are 



34<$ ELEMENTARY ZOOLOGY 

strictly maritime. The albatrosses are very large, the 
largest being three feet long with a spread of wing of 
seven feet. They are often found flying easily over the 
open ocean at great distances from land. Like the auks 
and puffins, the fulmars and shearwaters gather in extra- 
ordinary numbers on rocky ocean islets or cliffs of the 
coast to breed. 

The cormorants, pelicans, etc. (Steganopodes). — The 
Steganopodes are water-birds with full-webbed feet, and 
prominent gular pouch, swimmers rather than flyers like 
the Longipennes. The cormorants {Phalacrocorax) in- 
habit rocky coasts and are green-eyed, large, heavy, 
black birds with greenish-purple and violet iridescence; 
they are among the most familiar of seashore birds. They 
feed chiefly on fish and dive and swim under water with 
great ability. Cormorants are rather gregarious, keeping 
together in small groups when fishing, migrating often in 
great flocks, and in the breeding season gathering in 
immense numbers on certain rocky cliffs or islets. They 
build their nests of sticks and sea-weed ; the eggs are 
three or four, and usually bluish green with white, chalky 
covering substance. 

The pelicans are large, long-winged, short-legged 
water-birds with enormous bill and large gular sac which 
is used as a dip-net to catch fish. There are three species 
in North America, the white pelican (Pelecamis erythro- 
rhynchus) occurring over most of the United States, the 
brown pelican {P. fuscus) of the Gulf of Mexico, and 
the California brown pelican {P. californicus) of the Pacific 
coast. 

An interesting member of this order is the famous 
frigate or man-of-war bird {Fregata aquila), with very long 
wings and tail and feet extraordinarily small. The 
frigates have the greatest command of wing of all the 
birds. They cannot dive and can scarcely swim or walk. 



BRANCH CHORD AT A; CLASS AVES : THE BIRDS 347 

The ducks, geese, and swans (Anseres).— The familiar 
wild ducks, of which there are forty species in North 
American fresh and salt waters ; the geese, of which there 
are sixteen species, and the three species of wild swans 
constitute the order Anseres. The bill in these birds is 
more or less flattened and is also lamellate, i.e. furnished 
along each cutting-edge with a regular series of tooth-like 
processes; the feet are webbed, and the body is heavy 
and flattened beneath. Of the fresh-w T ater or inland 
ducks, the more familiar are the mallard {Anas boschas) y 
a large duck w T ith head (male) and upper neck rich glossy 
green; the blue-winged teal {Querquedula discors) and 
green-winged teal {Nettion carolinense) ; the shoveller 
{Spatula clypeatd) with spoon-shaped bill ; the beautiful 
crested wood-duck {Aix spoils a) \ the expert diver, the 
plump little ruddy duck {Erismatnra rubtdd), and others. 
Of the coastwise ducks, the canvas-back {Aythya val- 
lisnerid) is famous because of its fine flavor, while among 
the strictly maritime ducks the eiders {Somaterid), which 
live in Arctic regions, are well known for their fine down. 
Of the geese, the commonest is the well-known Canada 
goose {Br ant a canadensis), while the pure- white snow- 
goose {Chen hyper bored), with black wing-feathers and 
red bill, is not unfamiliar. The wild swans {Olor) are the 
largest birds of the order, and are less familiar than the 
ducks and geese. 

The ibises, herons, and bitterns (Herodiones). — The 
tall, long-necked, long-legged, wading birds, known as 
herons and ibises, compose a small order, the Herodiones, 
of which but few representatives are at all familiar. 
Perhaps the most abundant species is the green heron 
{Ardea virescens) or " fly-up-the-creek, ' : one of the 
smaller members of the order. The crown, back, and 
wings are green, the neck purplish cinnamon, and the 
throat and fore neck white-striped. This bird is com- 



34$ ELEMENTARY ZOOLOGY 

monly seen perching on an overhanging limb, or flying 
slowly up or down some small stream. The great blue 
heron (Ardea herodias) is common over the whole 
country. It is four feet long and grayish blue, marked 
with black and white. It may be seen standing alone in 
wet meadows or pastures, or flying heavily, with head 
drawn back and long legs outstretched. It breeds 
singly, but oftener in great heronries, in trees or bushes. 
Its large bulky nests contain three to six dull, greenish- 
blue eggs about two and one-half inches long. The white 
egrets of the Southern States are shot for their plumes and 
have been locally exterminated in some places. The 
night-herons (Nycticorax) differ from the other forms in 
having both the neck and legs short. The bittern 
(Botaurus lentiginosus), Indian hen, stake-driver, or 
thunder-pumper, as it is variously called, is a familiar 
member of the order, found in marshes and wet pastures, 
and known by its extraordinary call, sounding like the 
' ' strokes of a mallet on a stake. ' : In color it is brownish, 
freckled and streaked with tawny whitish and blackish. 
Its nest is made on the ground; its eggs, from three to 
five in number, are brownish drab and about two inches 
long. 

The cranes, rails, and coots (Paludicolae). —The cranes, 
of which three species are known in North America, are 
large birds with long legs and neck, part of the head being 
naked or with hair-like feathers. The rare whooping 
crane (Grits americand) is pure white with black on the 
wings, and is fifty inches long from tip of bill to tip of 
tail. The sand-hill crane (G. mexicand) is slaty gray or 
brownish in color, never white, and although rare in the 
East is quite common in the South and West. Cranes 
build nests on the ground, and lay but two eggs, about 
four inches long, brownish drab in color with large irreg- 
ular spots of dull chocolate-brown. 



BRANCH CHORD AT A; CLASS AVES : THE BIRDS 349 

The rails are smaller than the cranes, with short wings 
and very short tail. They live in marshes and swamps, 
and in flying let the legs hang down. Their legs are 
strong, and for escape they trust more to speed in running 
than to flight. They are hunted for food. The most 
abundant rail is the " Carolina crake' or " sora " 
{Porzana Carolina), small and olive-brown with numerous 
sharp white streaks and specks. Many of these birds are 
shot each year during migration in the reedy swamps of 
the Atlantic States. The American coot or mud-hen 
(Fnlica amcricana), dark slate-color with white bill, is one 
of the most familiar pond-birds over all temperate North 
America. Its nest consists of a mass of broken reeds 
resting on the w T ater ; the eggs number about a dozen, 
and are clay-color with pin-head dots of dark brown. 

The snipes, sandpipers, plover, etc. (Limicolas). — The 
large order Limicolae, the shore-birds, includes the 
slender-legged, slender-billed, round-headed, rather 
small wading birds of shores and marshes familiar to 
us as snipes, plovers, sandpipers, curlews, yellow-legs, 
sandpeeps, turnstones, etc. Most of them are game- 
birds, such forms as the woodcock and Wilson's or 
English snipe being much hunted. The food of these 
birds consists of worms and other small animals, which 
are chiefly obtained by probing with the rather flexible, 
sensitive, and usually long bill in the mud or sand. The 
killdeer {sEgialitis vocifercL), familiar to all in its range 
by its peculiar call and handsome markings, the upland 
or field plover {Bartramia longicaudd), with its long legs 
and melodious quavering whistle, the tall, yellow-shanked 
" telltale ' or yellow-legs {Tot amis melanoleiicus) of the 
marshes and wet pastures, are among the most wide- 
spread and familiar species of the order. On the seashore 
the dense flocks of white-winged, whisking sandpipers 
and the quickly running groups of plump ring-necked 



35° ELEMENTARY ZOOLOGY 

plover are familiar sights. One of the largest birds of 
this order is the long-billed curlew (Numenius longirostris) 
of the upland pastures. The bill of the curlew is long 
and curved downwards. The nests of these shore-birds 
are made on the ground and are usually little more than 
shallow depressions in which the few spotted eggs (four 
is a common number) are laid. The young are precocial. 
The grouse, quail, pheasants, turkeys, etc. (Gallinae). 
— The Gallinae include most of the domestic fowls, as the 
hen, turkey, peacock, guinea-fowls, and pheasants, and 
the grouse, quail, partridges, and wild turkeys. The 
chief game-birds of most countries belong to this order. 
They have the bill short, heavy, convex, and bony, 
adapted for picking up and crushing seeds and grains 
which compose their principal food. Their legs are strong 
and usually not long, and are often feathered very low 
down. The Gallinae are mostly terrestrial in habit and 
are sometimes known as the Rasores or " scratchers. " 
Among the more familiar wild gallinaceous birds are the 
quail or " Bob white " {Colinus virginianns), abundant in 
eastern and central United States, the ruffed grouse 
{Bonasa umbellus) of the Eastern woods, and the prairie- 
chicken (Tympanuchus americamis) of the Western prairies. 
The sage-hen (Centrocercus uropliasianus), the largest of 
the American grouse, reaching a length of two and one- 
half feet, is an interesting inhabitant of the sterile sage- 
brush plains of the West. The ptarmigan (Lagopus) or 
snow-grouse, represented by several species, are found 
either among the rocks and snow-banks above timber 
line on high mountains, or in the Arctic regions. In 
summer their plumage is brown and white ; in winter they 
turn pure white to harmonize with the uniform snow- 
covering. On the Pacific coast are several species of 
quail, all differing much from those of the East. These 
Western species have beautiful crests of a few or several 



BRANCH CHORD AT A; CLASS AVES : THE BIRDS ' 35 * 

long plume-feathers, the body-plumage being also un- 
usually beautiful. The eggs of all the Gallinae are numer- 
ous and are laid in a rude nest or simply in a depression 
on the ground. In many of the species polygamy is the 
rule. The young are precocial. 

The doves and pigeons (Columbae). — The doves and 
pigeons constitute a small order, the Columbae, closely 
related to the Gallinae. A distinguishing characteristic 
of the Columbae lies in the bill, which is covered at the 
base with a soft swollen membrane or cere in which the 
nostrils open. The members of this order feed on fruits, 
seeds, and grains. Our most familiar wild species is the 
mourning-dove or turtle-dove (Ze?iaidura macroiira) found 
abundantly all over the country. It lays two eggs in a 
loose slight nest in a low tree or on the ground. The 
beautiful wild or passenger pigeon (Ectopistes migratorius) 
was once extremely abundant in this country, moving 
about in tremendous flocks in the Eastern and Central 
States. But it has been so relentlessly hunted that the 
species is apparently becoming extinct. In the Rocky 
and Sierra Nevada mountains is a rather large dove, the 
band-tailed pigeon (Columba fasciata), which subsists 
chiefly on acorns. The domestic pigeon represented by 
numerous varieties, pouters, carriers, ruff-necks, fan-tails, 
etc., is the artificially selected descendant of the rock-dove 
{Columba livid). The young of all pigeons are altricial. 

The eagles, owls, and vultures (Raptores).— The 
"birds of prey " compose one of the larger orders, the 
members of which are readily recognizable. In all the 
bill is heavy, powerful, and strongly hooked at the tip. 
The feet are strong, with long, curved claws (small in the 
vultures) and are fitted for seizing and holding living 
prey, such as smaller birds, fish, reptiles, and mammals 
which constitute the principal food of the true raptorial 
species. The vultures feed on carnon. The turkey 



352 



ELEMENTARY ZOOLOGY 



buzzard {Cat hart es aura) is the most familiar of the three 
species of carrion-feeding Raptores found in the United 
States. The buzzard nests on the ground or in hollow 
stumps or logs, and lays two white eggs (sometimes only 
one) blotched with brown and purplish. The largest 
North American vulture is the California condor {Psendo- 
grypJius calif orniamis), which attains a length of four and 
one-half feet, with a spread of wing of nine and one-half 




Fig. 138.-— Screech-owl, Megascops asio. (Photograph by A. L, Princetorr 
permission of Macmillan Co.) 

feet. Of the eagles, the most widespread and commonest 
is the bald eagle {Halicetus leucocephalus). It is three 
feet long and when adult has the head and neck w r hite. 
The golden eagle {Aquila cJiryscetos) has the neck and 
head tawny brown. Of the many species of hawks, the 
marsh harrier {Circus hudsonins), abundant all "over the 
country and readily known by its white rump, is one of 



BRANCH CHORD AT A: CLASS AVES : THE BIRDS 353 

the most familiar. The name " chicken-hawk " is given 
to two or three different species of large broad-winged 
hawks of the genus Butco. The stout little sparrow-hawk 
{Falco sparverins), common over the whole country, is 
familiar and readily recognizable by its pronounced bluish 
and black wings and black-and-white banded chestnut 
tail. Altogether fifty species of hawks and eagles are 
found in this country. Of the owls, the barn-owl {Strix 
pratiucola) with its long triangular face and handsome 
mottled and spotted tawny coat is more or less familiar . 
the great horned owl [Bubo virginianus), the snowy owl 
(Nyctea nycted), and the great gray owl (Scotiaptex 
cinered) are the common large species, while the red 
screech-owl (Megascops asid) (fig. 138), the most abundant 
owl in the country, and the strange burrowing owl 
(Speotyto cuniciilarid), which lives in the holes of prairie- 
dogs and ground-squirrels in the West, are familiar smaller 
ones. Thirty-two species of owls are recorded from 
North America. 

The parrots (Psittaci). — The parrots, of which only 
one species is native in the United States, constitute an 
interesting order of birds, the Psittaci. They are abun- 
dant in tropical America. They have a very thick 
strongly hooked bill, with a thick and fleshy tongue. 
The feet have two toes pointing forward and two back- 
ward. The plumage is usually brightly and gaudily 
colored. The natural voice is harsh and discordant, but 
many of the species can imitate with surprising cleverness 
the speech of man. Parrots are long-lived and usually 
docile, and are much kept as pets. The single native 
species, the Carolina paroquet (Conurus carolinensis), is 
about a foot in length, is green, with yellow head and 
neck and orange-red face. Its range once extended from 
the Gulf of Mexico north to the Great Lakes, but it has 
been nearly exterminated in all the States but Florida. 



354 ELEMENTARY ZOOLOGY 

The cuckoos and kingfishers (Coccyges). — The 

cuckoos and kingfishers are regarded as constituting an 
order, Coccyges, a small group whose members are with- 
out any definite bond of union. Only ten species of North 
American birds belong to this order. The yellow-billed 
and black-billed cuckoos (Coccyzus) or " rain-crows " are 
long-tailed, slender, lustrous drab birds, which lay their 
eggs in the nests of others. They are notable for their 
peculiar rolling call. On the plains and hills of California 
and the southwest lives the road-runner or chaparral cock 
(Geococcyx calif orniamis), a strange bird belonging to the 
cuckoo family. It is nearly two feet long, of which length 
the tail makes half. These birds run so rapidly that a 
horse is little more than able to keep up with them. They 
feed on fruits, various reptiles, insects, etc. The one 
common kingfisher of this country, the belted kingfisher 
{Ceryle alcyon), a thick-set, heavy-billed, ashy blue-and- 
white bird, is familiar along streams. As it flies swiftly 
along it gives its rattling cry. It nests in deep holes in 
the stream-banks, and lays six or eight crystal-white 
spheroidal eggs. 

The woodpeckers (Pici). — The familiar woodpeckers 
and sap-suckers compose a well-defined order, Pici, which 
is represented in North America by twenty-five species. 
The bill of the woodpecker is stout and strong, usually 
straight, fitted for driving or boring into wood ; the tongue 
is long, sharp-pointed, and barbed, fitted for spearing 
insects. The feet have two toes turned forward and two 
backward; the tail-feathers are stiff and sharp-pointed 
and help support the bird as it clings to the vertical side 
of a tree-trunk or branch (fig. 139). The food of most 
woodpeckers consists chiefly of insects, usually wood- 
boring larvae (grubs). These birds do much good by 
destroying many noxious insect pests of trees. A few 
species, the true sap-suckers, probably feed on the sap of 



BRANCH CHORD AT A; CLASS AVES : THE BIRDS 355 



trees. Their nests are made in holes in trees, and the 
eggs are pure white and rounded. The harsh and shrill 
cries of the woodpeckers are familiar to all. 

The largest and one of the most interesting wood- 
peckers is the ivory-billed {CampepJiilus principalis), 
twenty inches long, glossy blue-black, with a high head- 




FlG. 139. — The yellow-hammer, Colaptes anratus. (Photograph by W. E. 
Carlin: permission of G. O. Shields.) 

crest which is scarlet in the male. This bird lives in the 
heavily wooded swamps of the Southern States. Among 
the more abundant and widespread, and hence better 
known, woodpeckers are the yellow-hammers (fig, 139) 



35 6 ELEMENTARY ZOOLOGY 

or flickers {Colaptes auratus in the East, C. cafer in the 
West), the red-headed woodpecker (Melanerpes erythro- 
cephahis), with its crimson head and neck and pure-white 
''vest"; and the black-and-white downy (Dryobatcs 
pubescens) and hairy (D. villosus) woodpeckers or ^sap- 
suckers. ' : The California woodpecker {M. formicivonts), 
a near relative of the red-headed woodpecker, has the 
curious habit of boring small holes in the bark of oak- or 
pine-trees and sticking acorns into these holes. Some- 
times thousands of acorns are put into the bark of one 
tree, to which the birds come occasionally to break open 
some acorns and feed on the grubs inside. 

The whippoorwills, chimney-swifts and humming- 
birds (Macrochires). — All the birds of this order are 
remarkable for their power of flight. They have long and 
pointed wings ; their feet are small and weak and used 
only for perching or clinging. All feed on insects, which 
are caught on the wing by the short-beaked, wide- 
mouthed swifts and whippoorwills and extracted from 
flower-cups by the humming-birds with their long and 
slender bills. The whippoorwill {Antrostomus vocif erics) 
is common in the woods of the East and is readily known 
by its call. Its two brown-blotched white eggs are laid 
loose on the ground or on a log or stump. The night- 
hawk {Chordeiles virginianus), common over the whole 
country, is seen at twilight flying vigorously about in 
its search for insects. Its nesting habits are like those 
of the whippoorwill. The sooty-brown chimney-swifts 
(Chcetura pelagica), popularly confused with the swallows, 
are the common inhabitants of old chimneys, in which they 
build their curious saucer-shaped open-work nests. Their 
eggs are pure white and number four or five. Of the 
humming-birds but one species, the ruby-throat (Trochilus 
colubris), is to be found in the Eastern States, but in the 
western and especially southwestern parts of the country 



BRANCH CHORD AT A; CLASS AVES : THE BIRDS 35 7 



several other species occur, 
have been found in the 
United States. The nests 
(fig. 140) of the hummers 
are very dainty little cups 
lined with hair or wool or 
plant -down. The ruby- 
throat lays two tiny pure- 
white eggs. 

The perchers (Passeres). 
— Nearly one-half of the 
birds of North America be- 
long to the great order Pas- 
seres, and of all the known 
birds of the world more than 
half are included in it. The 
Passeres or perching birds 
include the familiar song- 
birds and a great majority 
of the birds of the garden, 
the forest, the roadside, and 
the field. The feet of these 
birds always have four toes 
and are fitted for perching. 
The syrinx or musical ap- 
paratus is, in most, well 
developed. The nesting 
and other domestic habits 
are various, but the young 

a 



In all seventeen species 



are always hatched in 

helpless condition and have fig. 140. 

to be fed and otherwise 




— Nest and eggs of ruby- 
throat humming "bird, Trochihis 
colubris, seen from above, in apple- 
Cared for by the parents for tree. (Photograph by E. G. Tabor; 
1 1 ,• permission of Macmillan Co. ) 

a longer or shorter time. v 

The North American species of this order are grouped into 



358 



ELEMENTARY ZOOLOGY 



eighteen families, as the fly-catcher family (Tyrannidae), 
the crow family (Corvidae), the sparrows and finches 
(Fringillidae), the swallows (Hirundinidae), the warblers 
(Mniotiltidae), the wrens (Troglodytidae), the thrushes, 
robins and bluebirds (Turdidae), etc. In this book 
nothing can be said of the various species which belong 
to this order. However, as the passerine birds are 






~l 







ft 



* 






% $ 






{ 



% 



m 



& 



- _ : 



Fig. 141. — Horned larks. Otocoris alpestris, and snowflakes, Pleclrophenax 
nivalis. (Photograph from life by H. W. Menke; permission of Mac- 
millan Co.) 

those which most immediately surround us and which, by 
their familiar songs and nesting habits, most interest us, 
the. out-door study of birds by beginning students will be 
devoted chiefly to the members of this order, and many 
species will soon be got acquainted with. The robin and 
bluebird will introduce us to the shyer and less familiar 
song-thrushes; the study of the kingbird or bee-martin 



BRANCH CHORD AT A; CLASS AVES : THE BIRDS 359 

will interest us in some of the other fly-catchers; from the 
familiar chipping sparrow and tree-sparrow we shall be 
led to look for their cousins the swamp-sparrows and 
song-sparrows, and the larger grosbeaks and cross-bills, 
and so on through the order. 

Determining and studying the birds of a locality.— 
To identify the various species of birds in the locality of 
the school it will be necessary to have some book giving 
the descriptions of all or most of the species of the region, 
with tables and keys for tracing out the different forms. 
Such manuals or keys are numerous now; the study of 
birds is one of the most popular lines of nature study, and 
a host of bird books has been published in the last few 
years. The best general manual is Coues's k4 Key to the 
Birds of North America," which includes not only keys 
for tracing and descriptions of all the known species of 
birds on this continent, but also accounts of the distribu- 
tion, of the nesting and eggs, and of the plumage of the 
young birds, besides a thorough introduction to the 
anatomy and physiology of birds, and directions for col- 
lecting and preserving them. Jordan's "Manual of 
Vertebrates ' gives keys and short descriptions of the 
birds found east of the Missouri River; Chapman's 
14 Handbook of the Birds of Eastern North America " is 
excellent. To be able to use these manuals it is neces- 
sary to have the bird's body in hand; and that means 
usually death for the bird. Recently there have been 
published several bird-keys which attempt to make it 
possible to determine species, the commoner ones at any 
rate, without such close examination. The birds in these 
books are usually grouped wholly artificially (without any 
reference to their natural relationships) according to such 
salient characteristics as color, markings, size, habit of 
perching, or running, or flying, etc. These characteris- 
tics are such as can presumably be made out in the living 



360 ELEMENTARY ZOOLOGY 

bird by aid of an opera-glass or often with the unaided eye. 
Such books make no pretence to be scientific manuals nor 
to include any but the more usual and strongly marked 
species. They are usually limited to the birds of a 
restricted region. Such books are readily obtainable. 
There are several popular illustrated "bird-magazines' 
devoted to accounts of the life and habits of birds. Of 
these " Bird-lore " is the organ of the Audubon Society 
for the Protection of Birds. 




Fig. 142. — Western chipping sparrow, Splzella socialis arizonae. (Photo- 
graph from life by Eliz. and Jos. Grinnell.) 

In trying to become acquainted with the birds of a 
locality it must be borne in mind that the bird-fauna of 
any region varies with the season. Some birds live in a 
certain region all the year through ; these are called resi- 
dents. Some spend only the summer or breeding season 
in the locality, coming up from the South in spring and 
flying back in autumn ; these are summer residents. Some 
spend only the winter in the locality, coming down from 



BRANCH CHORD AT A; CLASS AVES : THE BIRDS 361 

the severer North at the beginning of winter and going 
back with the coming of spring; these are winter resi- 
dents. Some are to be found in the locality only in spring 
and autumn as they are migrating north and south 
between their tropical winter quarters and their northern 
summer or breeding home; these are migrants. And 
finally an occasional representative of certain bird species 
whose normal habitat does not include the given locality 
at all will appear now and then blown aside from its 
regular path of migration or otherwise astray; these are 
visitants. As to the relative importance, numerically, 
of these various categories among the birds which may be 
found in a certain region and thus form its bird-fauna we 
may illustrate by reference to a definite region. Of the 
351 species of birds which have been found in the State 
of Kansas (a region without distinct natural boundaries 
and fairly representative of any Mississippi valley region 
of similar extent), 51 are all-year residents; 125 are 
summer residents; 36 are winter residents; 104 are 
migrants ; and 35 are rare visitants. 

It must also be kept in mind in using bird-keys and 
descriptions to determine species that the descriptions and 
keys refer to adult birds, and in ordinary plumage. 
Among numerous birds the young of the year, old enough 
to fly and as large as the adults, still differ considerably 
in plumage from the latter; males differ from females, 
and finally both males and females may change their 
plumage (hence color and markings) with the season. 
The seasonal changes of plumage accomplished by molt- 
ing may be marked or hardly noticeable. 4l All birds 
get new suits at least once a year, changing in the fall. 
Some change in the spring also, either partially or wholly, 
while others have as many as three changes — perhaps, to 
a slight extent, a few more. ... It is claimed by some 
that now all new colors are acquired by molt, and by 



o 



62 ELEMENTARY ZOOLOGY 



others that in some instances (young hawks) an infusion 
or loss, as the case may be, of pigment takes place as the 
feather forms, and continues so long as it grows." 

There is much lack and uncertainty of knowledge con- 
cerning the molting and change of plumage by birds, and 
careful observations by bird-students should be made on 
the subject. 

In connection with learning the different kinds of birds 
in a locality, together with their names, observations 
should be made, and notes of them recorded, on their 
habits and on the relation or adaptation of structure and 
habit to the life of the bird. Some of the special subjects 
for such observation are pointed out in the following 
paragraphs. A suggestive book, treating of the adapt- 
ive structure and the life of birds is Baskett's * 4 The 
Story of the Birds." 

Bills and feet. — The interesting adaptation of struc- 
ture to special use is admirably shown in the varying 
character of the bills and feet of birds. The various feed- 
ing habits and uses of the feet of different birds are readily 
observed, and the accompanying modification of bills 
and feet can be readily seen in birds either freshly killed 
or preserved as 4i bird-skins. " Such skins may be made 
as directed on p. 467, or may be bought cheaply of 
taxidermists. A set of such skins, properly named, will 
be of great help in studying birds, and should be in the 
high-school collection. In some cases the general struc- 
ture of feet and bills may be seen in the live birds by the 
use of an opera-glass. The characters of bills and feet 
are much used in the classification of birds, so that any 
knowledge of them gained primarily in the study of 
adaptations will have a secondary use in classification work. 

Note the foot of the robin, bluebird, catbird, wrens, 
warblers and other passerine or perching birds. It has 
three unwebbed toes in front, and a long hind toe per- 



BRANCH CHORD AT A; CLASS AVES : THE BIRDS 363 

fectly opposable to the middle front one. This is the 
perching foot. Note the so-called zygodactyl foot of the 
woodpecker, with two toes projecting in front and partly 
yoked together, and two similarly yoked projecting 
behind. Note the webbed swimming foot of the aquatic 
birds; note the different degrees of webbing, from the 
totipalmate, where all four toes are completely webbed, 
palmate, where the three front toes only are bound 




Fig. 143. — Russet- backed thrush, Turdus ustulatus. 
life by Eliz. and Jos. Grinnell.) 



(Photograph from 



together but the web runs out to the claws, to the semi- 
balmate, where the web runs out only about half way. 
Note the lobate foot of the coots and phalaropes. Note 
the long slender wading legs of the sandpipers, snipe 
and other shore birds ; the short heavy strong leg of the 
divers; the small weak leg of the swifts and humming 
birds, almost always on the wing; the stout heavily nailed 
foot of the scratchers, as the hens, grouse, and turkeys; 
and the strong grasping talons, with their sharp long 



364 ELEMENTARY ZOOLOGY 

curving nails, of the hawks and owls and other birds of 
prey. In all these cases the fitness of the structure of the 
foot to the special habits of the bird is apparent. 

Similarly the shape and structural character of the bill 
should be noted, as related to its use, this being chiefly con- 
cerned of course with the feeding habits. Note the strong 
hooked and dentate bill of the birds of prey; they tear 
their prey. Note the long slender sensitive bill of the 
sandpipers ; they probe the wet sand for worms. Note 
the short weak bill and wide mouth of the night-hawk 
and whippoorwill and of the swifts and swallows; they 
catch insects in this wide mouth while on the wing. Note 
the flat lamellate bill of the ducks; they scoop up mud 
and water and strain their food from it. Note the firm 
chisel-like bill of the woodpeckers ; they bore into hard 
wood for insects. Note the peculiarly crossed mandibles 
of the cross-bills; they tear open pine-cones for seeds. 
Note the long sharp slender bill of the humming-birds; 
they get insects from the bottom of flower-cups. Note 
the bill and foot of any bird you examine, and see if they 
are specially adapted to the habits of the bird. 

The tongues and tails of birds are two other structures 
the modifications and special uses of which may be readily 
observed and studied. Note the structure and special use 
of the tongue and tail of the woodpeckers ; note the 
tongue of the humming-bird; the tail of the grackles. 

Flight and songs. — The most casual observation of 
birds reveals differences in the flight of different kinds, so 
characteristic and distinctive as to give much aid in 
determining the identity of birds in nature. Note the 
flight of the woodpeckers ; it identifies them unmistakably 
in the air. Note the rapid beating of the wings of quail 
and grouse ; also of wild ducks ; the slow heavy flapping 
of the larger hawks and owls and of the crows ; and the 
splendid soaring of the turkey-buzzard and of the gulls. 



BRANCH CHORD AT A; CLASS AVES : THE BIRDS 365 

This soaring has been the subject of much observation 
and study but is still imperfectly understood. The soaring 
bird evidently takes advantage of horizontal air-currents, 
and some observers maintain that upward currents also 
must be present. The principal hopes for the invention 
of a successful flying-machine rest on the power of soaring 
possessed by birds. The speed of flight of some birds is 
enormous, the passenger-pigeon having been estimated 




Fig. 144. — Oriole's nest with skeleton of blue jay suspended from it; the 
blue jay probably came to the nest to eat the eggs, became entangled 
in the strings composing the nest, and died bv hanging. (Photograph 
by S. J. Hunter.) 

to attain a speed of one hundred miles an hour. The 
long distances covered in a single continuous flight by 
certain birds are also extraordinary, as is also the total 
distance covered by some of the migrants. "It is said 
that some plovers that nest in Labrador winter in Pata- 
gonia, their long wings easily carrying them this great 
distance. " 



$66 ELEMENTARY ZOOLOGY 

Varying even more than the mariner and power of 
flight among different birds are the vocal utterances, the 
cries and calls and singing. By their calls and songs 
alone many birds may be identified although they remain 
unseen. The field-student of birds comes to know them 
by their songs; knows what birds they are; knows what 
they are doing or not doing; knows what time in their 
life-season it is, whether they are mating, or brooding, or 
preparing to migrate; knows whether they are frightened, 
or self-confident, whether in distress or happy. Little 
urging and suggestion are needed to induce the student 
to attend to the songs. But the naturalist should not 
only hear and enjoy them, but by observation and the 
recording of repeated observations, he should come to 
understand the significance of the calls and songs. 

As to how these sounds are made, attention has already 
been called (see p. 338) to the voice-organ or syrinx. 
The condition of this organ varies much in birds, as 
w r ould be expected from the differing character of vocal 
utterances. Dissections will make these differences 
apparent. 

Nesting and care of young. — Among the birds' most 
interesting instincts and habits are those domestic ones 
which include mating, nest-building, and care of the 
young. Birds' eggs and birds' nests are always attrac- 
tive objects of search and collection for boys, and most 
boys have a considerable personal knowledge of the 
domestic habits of the commoner summer birds of their 
region. With this interest and unsystematized knowledge 
as a basis the teacher should be able to get from the class 
much excellent field-work and personal observation. The 
first thing to undertake in this study is the gathering of 
data regarding the character of the nests of different 
species, their situation, the time of nesting, the participa- 
tion or non-participation of the male in nest-building, 



BRANCH CHORD AT A; CLASS AVES : THE BIRDS 367 

etc. ; also the number of eggs, their size and color mark- 
ings, the length of incubation, the help or lack of help of 
the male in brooding, etc. In connection with this 
gathering of data in the field by note-taking, sketching, 
and photographing, nests and eggs can be collected (see 
directions on page 469). Let only one clutch of eggs cf 
each species be taken for the common high-school collec- 
tion, and if more than one nest is desired take used and 
deserted nests. When the nestlings are hatched, the 
bringing of food, the defence of the home, and the teach- 
ing of the young to fly should all be observed and noted. 

Some attempt should be made to systematize the mis- 
cellaneous data obtained. Do all the members of a group 
have similar nesting habits ? Note the early nesting of 
birds of prey ; note the nests of the woodpeckers in holes 
in trees; note the nesting of the various swallows. Is 
there any significance in the colors and markings of eggs ? 
Observe the protective coloration obvious in some (see 
Chap. XXXI). Are there differences in the condition of 
the newly hatched nestlings ? Note the helpless altricial 
young of the robin ; the independent precocial young of 
the quail. 

The strong influence of the mating passion will be 
made plain by observations on the fighting, love-making, 
singing, and general behavior of the birds in the mating 
season. The expression of the mental and emotional 
traits, the psychic phenomena of birds, are most empha- 
sized at this time, and reveal the possession among 
animals lower than man of many characteristics which are 
too commonly ascribed as the exclusive attributes cf the 
human species. 

Local distribution and migration. — As explained in 
Chapter XXXII, the geographical distribution of animals 
is a subject of much importance, and offers good oppor- 
tunities in its more local features for student field-work. 



368 ELEMENTARY ZOOLOGY 

The field-study of the birds of a given locality will comprise 
much observation bearing directly on zoogeography or 
the distribution of animals. Certain birds will be found 
to be limited to certain parts of even a small region, the 
swimmers will be found in ponds and streams and the 
long-legged shore-birds on the pond- or stream-banks, or 
in the marshes and wet meadows, although a few like the 




Fig. 145. — Western robin, Merula migratoria propinqua. (Photograph from 
life by Eliz. and Jos. Grinnell. ) 

upland plover, curlews, and godwits are common on the 
dry upland pastures. Distinguish the ground-birds from 
the birds of the shrubs and hedge-rows and these again 
from the strictly forest-birds. Find the special haunts of 
swallows and kingfishers. Which are the sfry birds 
driven constantly deeper into the wild places or being 
exterminated by the advance of man ; which birds do not 



BRANCH CHORD AT A; CLASS AVES : THE BIRDS 3 6 9 

retreat but even find an advantage in man's seizure of the 
land, obtaining food from his fields and gardens ? 

Make a map on large scale of the locality of the school, 
showing on it the topographic features of the region, such 
as streams, ponds, marshes,- hills, woods, springs, wild 
pastures, etc., also roads and paths, and such landmarks 
as schoolhouses, county churches, etc. On this map in- 
dicate the local distribution of the birds, as determined 
by the data gradually gathered ; mark favorite nesting- 
places of various species, roosting-places of crows and 
blackbirds, feeding-places, and bathing- and drinking- 
places of certain kinds, the exact spots of finding rare 
visitants, rare nests, etc., etc. The making of such a 
zoogeographical map will be a source of great interest 
and profit to the students. 

As already mentioned, many of the birds of a locality 
are " migrants, that is, they breed farther north, but 
spend the winter in more southern latitudes. These 
migrants pass through the locality twice each year, going 
north in the spring and south in the autumn. They are 
much more likely to be observed during the spring migra- 
tion than in the fall, as the flight south is usually more 
hurried. The observation of the migration of birds is 
very interesting, and much can be done by beginning 
students. Notes should be made recording the first time 
each spring a migrating species is seen, the time when it 
is most abundant and the last time it is seen the same 
spring. Similar records should be made showing the 
movements of the birds in the fall. A series of such 
records covering a few years will show which are the 
earliest species to appear, w^hich the later, and which the 
last. Such records of appearance and disappearance 
should also be kept for the summer residents, those birds 
that come from the South in the spring, breed in the 
locality, and then depart for the South again in the 



37° ELEMENTARY ZOOLOGY 

autumn. Notes on the kinds of days, as stormy, clear, 
cold, warm, etc., on which the migration seems to be 
most active ; on the greater prevalence of migratory flights 
by day or by night ; on the height from the earth at which 
the migrants fly, etc., are all worth while. The Division 
of Biological Survey, U. S. Department of Agriculture, 
keeps records of notes on migration sent in by voluntary 
observers and furnishes blanks to be filled out by each 
observer. A suggestive book about migration, and one 
giving the records for many species at many points in the 
Mississippi valley is Cooke's "Bird Migration in the 
Mississippi Valley.' Migration is discussed in most bird- 
books. 

Feeding habits, economics, and protection of birds. — 
The feeding habits of birds are not only interesting, but 
their determination decides the economic relation of birds 
to man, that is, whether a particular bird species is harm- 
ful or beneficial to man. Casual observation shows that 
birds eat worms, grains, seeds, fruits, insects. A single 
species often is both fruit-eating and insect-eating. Do 
fruits or do insects compose the chief food-supply of the 
species ? To determine this more than casual observation 
is necessary. The birds must be watched when feeding 
at different seasons. The most effective way of determin- 
ing the kind of food which the bird takes is to examine 
the stomachs of many individuals taken at various times 
and localities. Much work of this kind has been done, 
especially by the investigators connected with the Division 
of Biological Survey of the U. S. Department of Agricul- 
ture, and pamphlets giving the results of these investiga- 
tions can be had from the Division. It has been distinctly 
shown that a great majority of birds are chiefly beneficial 
to man by eating noxious insects and the seeds of weeds. 
Many birds commonly reputed to be harmful, and for that 
reason shot by farmers and fruit-growers, have been 



BRANCH CHORD AT A; CLASS AVES : THE BIRDS 371 

proved to do much more good than harm. Some few 
birds have been proved to be, on the whole, harmful. 
An investigation of the food habits of the crow, a bird of 
ill-repute among farmers, based on an examination of 909 
stomachs shows that about 29 per cent of the food for the 















1 

s - 

l 








\*m 











Fig. 146. — Sickle-billed thrasher, Harporhynchus redevivtis. (Photograph 
from life by Eliz. and Jos. Grinnell.) 



year consists of grain, of which corn constitutes something 
more than 21 per cent, the greatest quantity being eaten 
in the three winter months. All of this must be either 
waste grain picked up in fields and roads, or corn stolen 
from cribs and shocks. May, the month of sprouting corn, 



372 ELEMENTARY ZOOLOGY 

shows a slight increase over the other spring and summer 
months. On the other hand the loss of grain is offset by 
the destruction of insects. These constitute more than 
23 per cent of the crow's yearly diet, and the larger part 
of them are noxious. The remainder of the crow's food 
consists of wild fruit, seeds and various animal substances 
which may on the whole be considered neutral. 

The slaughter of birds for millinery purposes has 
become so fearful and apparent in recent years that a 
strong movement for their protection has been inaugu- 
rated. Rapacious egg-collecting, legislation against 
birds wrongly thought to be harmful to grains and fruit, 
and the selfish wholesale killing of birds by professional 
and amateur hunters, help in the work of destruction. 
Apart from the brutality of such slaughter, and the ex- 
termination of the most beautiful and enjoyable of our 
animal companions, this destruction * works strongly 
against our material interests. Birds are the natural 
enemies of insect pests, and the destroying of the birds 
means the rapid increase and spread, and the enhanced 
destructive power of the pests. It is asserted by investi- 
gators that during the past fifteen years the number of our 
common song-birds has been reduced to one-fourth. At 
the present rate, says one author, extermination of many 
species will occur during the lives of most of us. Already 
the passenger-pigeon and Carolina paroquet, only a few 
years ago abundant, are practically exterminated. Protect 
the birds ! 

* One of the most unfortunate and conspicuous examples of this slaughter 
is the partial extermination of the song-birds of Japan in the interests of 
European milliners. To meet their demands the country people used bird- 
lime throughout the woods with disastrous effectiveness, as shown in the 
present exceeding scarcity of birds and the abundance of insect pests. 



CHAPTER XXVIII 

BRANCH CHORDATA [Continued). CLASS MAM- 
MALIA: THE MAMMALS 

THE MOUSE {Mus musculus) 

Technical Note. — It is best to catch specimens alive in a good 
trap. A live trap well baited and placed in some old granary 
should furnish plenty for class use. White mice can often be ob- 
tained at " bird-stores." When mice are not procurable, use rats. 
A rat is perhaps preferable on account of its size, but all essential 
structures can readily be made out in the mouse. Specimens 
should be killed by chloroform as described for the toad, p. 5. 

Structure (fig. 147). — Compare the external characters 
of the mouse with those of the toad and sparrow. The 
mouse, unlike the other vertebrates so far studied, is thickly 
covered with hair all over its body except on the tip of 
the nose and the soles of the feet. Where are the nostrils 
placed ? What are the large leaf-like expansions called 
pinnce situated just back of the eyes ? Pull open the 
mouth and note the large incisor teeth on the upper and 
lower jaws. Cut one corner of the mouth back and 
observe the large flat-topped molar teeth on both jaws. 
How does the attachment of the large fleshy tongue differ 
from the condition in the toad ? The toad's tongue is for 
snapping up insects, whereas in the mouse this organ 
serves to move food about in the mouth. On the tongue 
are numerous small taste-papillae. Notice the long hairs, 
14 feelers," on each side of the nose. Note the similarity 
between the front paws and our own hands ; each has 
four fingers with a small rudimentary thumb on the inner 

373 



374 ELEMENTARY ZOOLOGY 

side of the paw. How does the hind foot of the mouse 
differ from the foot of man ? Posteriorly the body is 
terminated by a long tail. At the root of the tail is a 
small aperture, the anus, and just below, or ventral to it, 
is the opening from the kidneys and reproductive organs. 

Technical Note. — Place the mouse on its back in a dissecting- 
pan and cut through the skin from anus to the lower jaw. Extend 
the legs, pin down each foot and pin out the cut edges of the 
skin. Now carefully cut forward through the body-wall from the 
anal region and on through the breast-bones and ribs. Pin each 
side out. 

Near the hindmost pair of ribs note a sheet of muscles, 
the diaphragm, which extends across the body-cavity, 
dividing it into an anterior portion, the thoracic cavity, 
and a posterior, the abdominal cavity. What are the most 
conspicuous organs in the thoracic cavity ? Leading 
anteriorly to the mouth-cavity is a long tube, the trachea, 
composed of a series of cartilaginous parts of rings placed 
end to end. Note at its anterior end the glottis and 
epiglottis. Insert a blowpipe into the glottis and inflate 
the lungs, which will fill all the otherwise unfilled space 
in the thoracic cavity. The abdominal cavity contains 
the viscera suspended in a fold of the lining membrane, as 
in the other vertebrates studied. Note lying against the 
diaphragm a large, red, glandular structure, the liver. 
Separate the two large lobes of the liver and expose the 
opalescent gall-bladder. By passing a canula into this 
and ligaturing, the cystic duct may be injected. Beneath 
the liver is a large loop-shaped expansion of the alimen- 
tary canal, the stomach. Arising from the right end of 
the stomach is the narrow duodenum, which gradually 
merges into the very much convoluted small intestine, or 
ileum, which is followed by the large intestine, or colon, 
the last part of which is a straight tube, the rectum. The 
small intestine occupies most of the space in the peri- 



BRANCH CHORD AT A: CLASS MAMMALIA 3 75 

toneal cavity. Within the loop of the pylorus will be 
found an irregular pinkish mass of tissue, the pancreas. 
Beneath the stomach on the left side of the body lies a 
very dark glandular mass not much unlike the liver but 
altogether detached from it. This structure is the spleen, 
a ductless gland. 

Note dorsally of the trachea a long tube passing through 
the diaphragm and connecting the mouth with the 
stomach. What is this tube ? Note the Eustachian tubes 
extending from the mouth to the ears. The median part 
of the roof of the mouth is the palate, hard in front, soft 
behind. A pair of small bodies at the sides of the soft 
palate near its hinder end are the tonsils. At the pos- 
terior angle of the lower jaw are glandular bodies, the sub- 
maxillary glands, which lead by a short duct anteriorly 
to open on the floor of the mouth. On the sides of the 
neck just below the ears are pink or yellowish bodies, the 
parotid glands, opening anteriorly in the sides of the 
mouth-cavity. These two sets of glands are collectively 
known as the salivary glands, the function of which is to 
secrete the saliva. Push apart the sub-maxillary glands 
and note below them overlying the trachea on either side 
two dark-red lobes connected by a band of tissue. These 
constitute the thyroid gland, another of the so-called 
ductless glands. Within the thoracic cavity anterior to 
the heart note a mass of pinkish tissue, the thymus gland. 
Observe the large masseter muscles, which cover the jaws. 
What is their function ? On either side of the neck lies a 
large blood-vessel, the external jugular vein, which col- 
lects blood from the head and carries it down to the heart. 
Note the large pectoral muscles which cover the breast and 
extend out into the arms, and which are so strong and 
highly developed in the sparrow. The head is supported 
by large muscles which run down the back of the neck 
to the ribs. Others are attached to the ribs, which they 



376 



ELEMENTARY ZOOLOGY 



raise and lower. These movements, together with the 
contraction of the diaphragm, cause the expansion and 

contraction of the thoracic cavity 
whereby the lungs are regularly filled 
and emptied. Note that the abdomen 
is covered by a double layer of mus- 
cular tissue, the outer part made up 
of the external oblique muscles, the 
inner by the internal oblique muscles. 
Examine the heart. How many 
auricles has it ? The ventricles in 
the mouse, as in the bird, are entirely 
separated, forming tw r o complete 
compartments, a right and a left 
ventricle. The blood flowing from 
the veins of the body is collected in 
the right auricle, thence it passes into 
the right ventricle, wdience it is con- 
Fig. 148. —Diagram of veyed to the lungs ; returning it flows 

through the left auricle into the left 
ventricle, whence it is forced through 
the arteries of the body. For a 
study of the circulatory system in 

the arrows show the di- , /r oX , , . 

rection of the current; mammals (fig. 148), a rat or a rabbit 
the shaded vessels should be injected by the teacher and 

carrv venous blood, the 

others arterial blood, an advanced text-book, as Parker s 
(From Kingsley.) t , Zootomy ' ' or Marshall and Hurst's 

" Practical Zoology," used as a guide. A sheep's heart 
is very good to cut open for a class demonstration. 

Make a drawing of the organs observed thus far in the 
dissection. 

The kidneys in the mouse are situated in the dorsal 
region next to the backbone. They consist of two bean- 
shaped smooth glands. From them a pair of ducts, the 
ureters y can be traced down to a median thin-walled 




the circulation of the 
blood in a mammal; a, 
auricles ; /, lung ; tv, 
liver; p, portal vein 
bringing blood from the 
intestine; v. ventricles; 



BRANCH CHORD AT A : CLASS MAMMALIA 



377 



muscular sac, the bladder. The bladder opens to the 
exterior of the body by means of a short tube, the 
urethra. Cut open a kidney longitudinal]}' and examine 
the cut surfaces. 

The two egg-glands of the female mouse lie in the 
median portion of the abdominal cavity, somewhat below 
the kidneys, and from the vicinity of each runs an egg- 
tube. These tubes meet below the bladder, and open to 
the exterior of the body through the aperture noted below 
the anus. In the posterior parts of these tubes lie until 
birth the developing embryos. 

Technical Note. — For a study of the nervous system place the 
specimen ventral side down and cut through the skull with the bone- 
cutters or heavy scissors, exposing the brain and spinal cord. 

Note the large brain (fig. 149), composed of small optic 
lobes, large cerebrum, cerebellum^ and medulla oblongata, 
followed by the long spinal cord. Note the nerves aris- 
ing from the brain and spinal cord. 

For a careful dissection of the mammalian nervous 
system a larger mammal, such as a cat or dog or rabbit, 
should be used. For guide use a text-book such as, for 
the dog, Howell's " Dissection of the Dog " ; for the cat, 
Reighard and Jennings' lt Anatomy of the Cat " ; and for 
the rabbit, Parker's " Zootomy " or Marshall and Hurst's 



Sunfisb 



Toad 



Snake 



Sparrow 



Mouse 



Olf. L. 
Cbr. 

Md. Br. 




Sp. Cd. 



Fig. 149. —Diagram of brains of vertebrates; Olf. Z., olfactory lobes; Cbr., 
cerebrum ; Md. Br., midbrain (optic lobes) ; CbL. cerebellum; Med. 
Ob., medulla oblongata; Sp. Cd., spinal cord. (From specimens.) 



37§ 



ELEMENTARY ZOOLOGY 



" Practical Zoology." Make a good preparation of the 
brain and preserve it for future use in some fluid like 
Fischer's fluid (see page 453). 

Technical Note. — Prepare a well-cleaned skeleton by boiling a 
specimen in a soap solution and thoroughly cleansing it (seep. 452). 

Note the very compact skeleton of the mouse. Note 
the closely sutured skall. How many cervical or neck 
vertebrce are there ? The ribs are attached to the thoracic 
vertebrce. How many pairs of ribs ? The bony thorax 
supports the shoulder-girdle and bones of the fore legs. 
The thorax is followed by a series of ribless vertebrae, the 
lumbar vertebrce, which in the posterior region of the body 
fuse with the pelvic girdle supporting the hind limbs. 
The body vertebrae are succeeded by the very much 
smaller caudal vertebrce. Compare the skeleton of the 
mouse with that of the bird; also witli that of the toad. 
For directions for a detailed study of the skeleton see in 
Parker's " Zootomy " an ac- 
count of the skeleton of the 
rabbit, pp. 263-286. 

Technical Note. — For the 
study of the eye (fig. 150) the 
teacher should obtain the eye of 
some large mammal, as the ox or 
sheep, with which to make a class 
demonstration. The eye of a 
rabbit or cat can of course be 
used. For an account of the verte- 
brate eye see Parker and Haswell's 
"Text-book of Zoology," Vol. II. 
pp. 103-107. For a study of the 
ear use a bird or mammal, and 
see pp. 107-110 of the same book. f ig . 150.— Diagram of vertebrate 

eye; c, choroid; i, iris; /, lens; n, 

Life-history and habits. °P tic nerve ; r > retina; s, sclerotic. 

^ . (From Kingsley.) 

— Ihe house-mouse is not a 

native of Nortli America, but was introduced into this 

country from Europe, to which, in turn, it came from Asia, 




BRANCH CHORD AT A : CLASS MAMMALIA 379 

its original habitat. The mouse came to this country in 
the vessels of early explorers. Similarly the brown and 
black rats, now so abundant all over North America, and 
members of the same genus as the mouse, were intro- 
duced from Europe. Accompanying man in his travels 
the mouse has spread from Asia until it is now to be 
found over the whole world. 

The habits of mice are well known ; their fondness for 
living in our homes and outbuildings makes them familiar 
acquaintances. Their food is varied ; they seem to thrive 
best, however, on a vegetable diet. Grains and nuts are 
favorite foods. The house-cat is their greatest enemy, 
but man takes advantage of their instinct to go into holes 
by constructing traps with funnel or tunnel entrances 
which, baited with cheese or other favorite food, are 
fatally attractive. In climbing, mice are aided by the 
tail. Their strong hind legs enable them to stand erect, 
and even to take Several steps in this posture. They can 
swim readily, although naturally they rarely take to 
water. Their special senses are keen, the senses of hear- 
ing and taste being unusually well developed. Their 
kl singing, " which has been the subject of much discussion, 
seems to be actually a voluntary and normal performance 
which, however, hardlv deserves to be called sinmncr but 
rather a slightly varied peeping or whistling. 

The mouse is a prolific mammal, producing from four 
to six times a vear broods of from four to eight voung. 
The mouse makes a cosy nest of straw, bits of paper, 
feathers, wool or other soft materials, and in this the 
vounsf are born. The newly born mice are verv small 
and are blind and helpless. They are odd little creatures, 
being naked and almost transparent. They grow rapidly, 
being covered with hair in a week, although not opening 
their eyes for about two weeks. A day or two after their 
eyes are open they begin to leave the nest, and hunt for 
food for themselves. 



3 8 ° ELEMENTARY ZOOLOGY 

OTHER MAMMALS 

The mammals constitute the highest group of animals, 
including man, the monkeys and apes, the quadrupeds, 
the bird-like bats and fish-like seals and whales; in all 
about 2500 species. They are found everywhere except 
on a few small South Sea islands. Only a few species, 
however, have a world-wide distribution. The name 
Mammalia is derived from the mammary or milk glands 
with which the females are provided and by the secretion 
of which the young of this class, born free in all but a 
few of the lowest forms, are nourished for some time after 
birth. In size mammals range from the tiny pigmy-shrew 
and harvest mouse, which can climb a stem of wheat, to 
the great sulphur-bottom whale of the Pacific Ocean, which 
attains a length of a hundred feet and a weight of many 
tons. Mammals differ from fishes and batrachians and 
agree with reptiles and birds in never having external 
gills ; they differ from reptiles and agree with birds in being 
warm-blooded and in having a heart with two distinct 
ventricles and a complete double circulation; finally, they 
differ from both reptiles and birds in having the skin more 
or less clothed with hair, the lungs freely suspended in a 
thoracic cavity separated from the abdominal by a mus- 
cular partition, the diaphragm, and in the possession by 
the females of mammary glands. In economic uses to 
man mammals are the most important of all animals. 
They furnish the greater portion of the animal food of many 
human races, likewise a large amount of their clothing. 
Horses, asses, oxen, camels, reindeer, elephants, and 
llamas are beasts of burden and draught; swine, sheep, 
cattle, and goats furnish flesh, and the two latter milk for 
food; the wool of sheep, the furs of the carnivores, and 
the leather of cattle, horses, and others are used for cloth- 
ing, while the bones and horns of various mammals serve 
various purposes. 







T 



BRANCH CHORD AT A: CLASS MAMMALIA 381 

Body form and structure. — The mammalian body 
varies greatly. Its variety of form and general organiza- 
tion is explained by the facts that, although most of the 
species live on the surface of the earth, some are burrowers 
in the ground, some flyers in the air, and some swimmers 
in the water. Mammals never have more than two pairs 
of limbs ; in most cases both pairs are well developed and 
adapted for terrestrial progression. In the aenal bats the 
fore limbs are modified into organs of flight; among the 
aquatic seals, sea-lions, walruses, and whales both sets are 
modified to be swimming flippers or paddles. In many 
of these aquatic forms the hind limbs are greatly reduced 
or even completely wanting. 

Most mammals are externally clothed with hair, which 
is a peculiarly modified epidermal process. Each hair, 
usually cylindrical, is composed of two parts, a central pith 
containing air, and an outer more solid cortex ; each hair 
rises from a short papilla sunk at the bottom of a follicle 
lying in the true skin. In some mammals the hairs 
assume the form of spines or ' ' quills, ' ' as in the porcupine. 
The hairy coat is virtually wanting in whales and is very 
sparse in certain other forms, the elephant, for example, 
which has its skin greatly thickened. The claws of beasts 
of prey, the hooves of the hoofed mammals, and the outer 
horny sheaths of the hollow-horned ruminants* are all 
epidermal structures. 

The bones of mammals are firmer than those of other 
vertebrates, containing a larger proportion of salts of lime. 
Among the different forms the spinal column varies largely 
in the number of vertebrae, this variation being chiefly 
due to differences in length of tail. Apart from the 
caudal vertebrae their usual number is about thirty. The 
mammalian skull is very firm and rigid, all the bones 
composing it, excepting the lower jaw, the tiny auditory 
ossicles, and the slender bones of the hyoid arch, being 



382 



ELEMENTARY ZOOLOGY 



immovably articulated together. The correspondence 
between the bones of the two sets of limbs is very ap- 
parent. The number of digits varies in different mammals, 
and also in the fore and hind limbs of a single species. 
Among the Ungulates the reduction in the number of 
digits is especially noticeable ; the forefoot of a pig has 
four digits, that of the cow two, and that of the horse one. 
The two short " splint " bones in the horse are remnants 
of lost digits. The teeth are important structures in 
mammals, being used not only for tearing and masticat- 
ing food, but as weapons of offence and defence. A tooth 
consists of an inner soft pulp (in old teeth the pulp may 
become converted into bone-like material) surrounded by 
hard white dentine or ivory, which is covered by a thin 
layer of enamel, the hardest tissue known in the animal 
body. A hard cement sometimes covers as a thin layer 
the outer surface of the root, and may also cover the 
enamel of the crown. The teeth in most forms are of 
three groups: {a) the incisors, with sharp cutting edges 
and simple roots, situated in the centre of the jaw; (b) the 
canines, often conical and sharp-pointed, next to the 
incisors; (V) next the molars, broad and flat-topped for 
grinding, and divided into premolars and true molars. 
There is great variety in the character and arrangement 
of these structures in mammals, their variations being 
much* used in classification. The number and arrange- 
ment of the teeth is expressed by a dental formula, as, for 
example, in the case of man 



2 - - 2 ii ,2 — 2 3 — 3 

3 - 3 



i— — , c , p , in- = 32. 

1 — 1 r 2 — 2 x — % 



The mouth is bounded by fleshy lips. On the floor of 
the mouth is the tongue, which bears the taste-buds or 
papillae, the organs of taste. The oesophagus, is always 
a simple straight tube, but the stomach, varies; greatly, 



BRANCH CHORD AT A: CLASS MAMMALIA 



38.3 




Fig. 151. — A group of Rocky Mountain sheep, or ''big horns," Oris cana- 
densis, including males, females and young. (Photograph by E. Willis 
from specimens mounted by Prof. L. L. Dyche, University of Kansas.) 



384 ELEMENTARY ZOOLOGY 

being usually simple, but sometimes, as in the ruminants 
and whales, divided into several distinct chambers. The 
intestine in vegetarian mammals is very long, being in a 
cow twenty times the length of the body. In the carni- 
vores it is comparatively short — in a tiger, for example, 
but two or three times the length of the body. 

The blood of mammals is warm, having a temperature 
of from 35 C. to 40° C. (95 F. to 104 F.). It is red 
in color, owing to the reddish-yellow, circular, non- 
nucleated blood-corpuscles. The circulation is double, 
the heart being composed of two distinct auricles and two 
distinct ventricles. Air is taken in through the nostrils 
or mouth and carried through the windpipe (trachea) and 
a pair of bronchi to the lungs, where it gives up its oxygen 
to the blood, from which it takes up carbonic-acid gas in 
turn. At the upper end of the trachea is the larynx or 
voice-box, consisting of several cartilages attaching by 
one end to the vocal cords and by the other to muscles. 
By the alteration of the relative position of these cartilages 
the cords can be tightened or relaxed, brought together 
or moved apart, as required to modulate the tone and 
volume of the voice. 

The kidneys of mammals are more compact and definite 
in form than those of other vertebrates. In all mammals 
except the Monotremes they discharge their product 
through the paired ureters into a bladder, whence the 
urine passes from the body by a single median urethra. 
Mammary glands, secreting the milk by w r hich the young 
are nourished during the first period of their existence 
after birth, are present in both sexes in all mammals, 
though usually functional in the female only. 

The nervous system and the organs of special sense 
reach their highest development in the mammals. In 
them the brain is distinguished by its large size, and by 
the special preponderance of the forebrain or cerebral 



BRANCH CHORDA TA : CLASS MAMMALIA 



H 




>^ 



u 

be 

o ^ 

~ 7i 



M 

a o 

*■! 

_, u 
c > 

li 






Si 



^ 



Oh 

C 
j 



»— » 



$86 ; ELEMENTARY ZOOLOGY , 

hemispheres over the mid- and hind-brain. Man's brain 
is many times larger than that of all other known mam- 
mals of equal bulk of body, and three times as large as 
that of the largest-brained ape. In man and the higher 
mammals the surface of the forebrain is thrown into many 
convolutions; among the lowest the surface is smooth. 
Of the organs of special sense, those of touch consist of 
free nerve-endings or minute tactile corpuscles in the skin. 
The tactile sense is especially acute in certain regions, as 
the lips and end of the snout in animals like hogs, the 
fingers in man, and the under surface of the tail in certain 
monkeys. All the other sense-organs are situated on the 
head. The organs of taste are certain so-called taste- 
buds located in the mucous membrane covering certain 
papillae on the surface of the tongue. The organ of 
smell, absent only in certain whales, consists of a ramifi- 
cation of the olfactory nerves over a moist mucous mem- 
brane in the nose. The ears of mammals are more highly 
developed than those of other vertebrates both in respect 
to the greater complexity of the inner part and the size 
of the outer part. A large outer ear for collecting the 
sound-waves is present in all but a few mammals. A 
tympanic membrane separates it from the middle ear in 
which is a chain of three tiny bones leading from the 
tympanum to the inner ear, composed of the three semi- 
circular canals and the spiral cochlea. The eyes (fig. 150) 
have the structure characteristic of the vertebrate eye, con- 
sisting of a movable eyeball composed of parts through 
which the rays of light are admitted, regulated, and con- 
centrated upon the sensitive expansion, retina, of the optic 
nerve lining the posterior part of the ball. The eye is pro- 
tected by two movable lids. In almost all mammals below 
the Primates there is a third lid, the nictitating membrane. 
In some burrowing rodents and others the eye is quite 
vestigial and even concealed beneath the skin^ 



BRANCH CHORD AT A: CLASS MAMMALIA 3 8 7 

Development and life-history. — All mammals except 
the Monotremes give birth to free young. The two 
genera of Monotremes produce their young from eggs 
hatched outside the body; Tacliyglossus lays one egg 
which it carries in an external pouch, while Ornithorhyn- 
fihus deposits two eggs in its burrow. The embryo of 
other mammals develops in the lower portion of the egg- 
lube y to the w r alls of which it is intimately connected by 
a membrane called the placenta. (In the kangaroos and 
opossums, Marsupialia, there is no placenta.) Through 
this placenta blood-vessels extend from the body of the 
mother to the embryo, the young developing mammal 
thus deriving its nourishment directly from the parent. 

The duration of gestation (embryonic or prenatal 
development in the mother's body) varies from three 
weeks with the mouse, eight weeks with the cat, nine 
months with the stag, to twenty months with the elephant. 
Like the birds, the young of some mammals, the carni- 
vores for example, are helpless at birth, while those of 
others, as the hoofed mammals, are very soon able to run 
about. But all are nourished for a longer or shorter time 
by the milk secreted by the mammary gland of the 
mother. 

Habits, instinct, and reason, — Despite the wonderful 
examples of instinct and intelligence shown by many 
insects and by the other vertebrates, especially the birds, 
it is among mammals that we find the highest develop- 
ment of these qualities and of reason. In the wary and 
patient hunting for prey by the carnivora, in the gregarious 
and altruistic habits of the herding hoofed mammals, in 
the highly developed and affectionate care of the young 
showm by most mammals, and in the loyal friendship and 
self-sacrifice of dogs and horses in their relations to man, 
we see the culmination among animals of the development 
of the functions of the nervous system. In the character- 



388 ELEMENTARY ZOOLOGY 

istics of intelligence and reason man of- course stands 
immensely superior to all other animals, but both intelli- 
gence and reason are too often shown by many of the 
other mammals not to make us aware that man's mental 
powers differ only in degree, not in kind, from those of 
other animals. 

Pure instinct is hereditary, and purely instinctive actions 
are common to all the individuals of a species. Those 
actions which the individual could not learn by teaching, 
imitation, or experience are instinctive. The accurate 
pecking at food by chicks just hatched from an incubator 
is purely instinctive. Purely instinctive also is the laying 
of eggs by a butterfly on a certain species of plant which 
may have to be sought for over wide acres, so that the 
caterpillars when hatched shall find themselves on their 
own special food-plant. Yet the butterfly never ate of 
this plant and will never see its young. Such elaborate 
instincts as these have been developed from the simplest 
manifestations of sensation and nervous function, just as 
the complex structures of the body have been developed 
from simple structures (see Chapter XXIX). 

The feeding and domestic habits and the whole general 
behavior of animals are extremely interesting subjects of 
observation and study. And such observation intelli- 
gently pursued will be of much value. The point to be 
kept ever in mind is that all animal habits are connected 
with certain conditions of life ; that in every case there is 
an answer to the question 4 ' why. ' : This answer may 
not be found ; in many cases it is extremely difficult to 
get at, but often it is simple and obvious and can be 
found by the veriest beginner. 

Classification. — The mammals of North America repre- 
sent eight orders. Three additional mammalian orders, 
namely, the Monotremata, including the extraordinary 
duck-bills {jDrnithorhynclius) and a species of Tachyglossus 



BRANCH CHORD AT A: CLASS MAMMALIA 3 8 9 

in Australia and Tasmania; the Edentata, including the 
sloths, armadillos, and ant-eaters found in tropical regions ; 
and the Sirenia, including the marine manatees and 
dugongs, are not represented (except by a single man- 
atee) in North America. In the following paragraphs 
some of the more familiar mammals representing each of 
the eight orders represented in North America are 
referred to. 

The opossums (Marsupialia). — The opossum (Didcl- 
pliys Virginia no) is the only North American representa- 
tive of the order Marsupialia, the other members of which 
are limited exclusively to Australia and certain neighbor- 
ing islands. The kangaroos are the best known of 
the foreign marsupials. After birth the young are trans- 
ferred to an external pouch, the marsupium, on the 
ventral surface of the mother, in which they are carried 
about and fed. The opossum lives in trees, is about the 
size of a common cat, and has a dirty-yellowish woolly 
fur. Its tail is long and seal}', like a rat's. Its food 
consists chiefly of insects, although small reptiles, birds, 
and bird's eggs are eaten. When ready to bear young 
the opossum makes a nest of dried grass in the hollow of 
a tree, and produces about thirteen very small (half an 
inch long) helpless creatures. These are then placed by 
the mother in her pouch. Here the}' remain until two 
months or more after birth. Probably all the North 
American opossums found from New r York to California 
and especially common in the Southern States belong to 
a single species, but there is much variety among the 
individuals. 

The rodents or gnawers (Glires).— The rabbits, porcu- 
pines, gophers, chipmunks, beavers, squirrels, and rats 
and mice compose the largest order among the mammals. 
They are called the rodents or gnawers (Glires) because 
of their well-known gnawing powers and proclivities. 



39o ELEMENTARY ZOOLOGY 

The special arrangement and character of the teeth are 
characteristic of this order. There are no canines, a 
toothless space being left between the incisors and molars 
on each side. There are only two incisor teeth in each 
jaw (rarely four in the upper jaw), and these teeth grow 
continuously and are kept sharp and of uniform length by 
the gnawing on hard substances and the constant rubbing 
on each other. The food of rodents is chiefly vegetable. 

Of the hares and rabbits the cottontail (Leptts nuttalli) 
and the common jack-rabbit (L. campestris) are the best 
known. The cottontail is found all over the United 
States, but shows some variation in the different regions. 
There are several species of jack-rabbits, all limited to the 
plains and mountain regions west of the Mississippi River. 
The food of rabbits is strictly vegetable, consisting of suc- 
culent roots, branches, or leaves. Rabbits are very 
prolific and yearly rear from three to six broods of from 
three to six young each. There are two North American 
species of porcupines, an Eastern one, Erethizon dorsatns, 
and a Western one, E. epixanthus. The quills in both 
these species are short, being only an inch or two in 
length, and are barbed. In some foreign porcupines they 
are a foot long. They are loosely attached in the skin 
and may be readily pulled out, but they cannot be shot 
out by the porcupine, as is popularly told. The little 
guinea-pigs (Cavid) y kept as pets, are South American 
animals related to the porcupines. 

The pocket gophers, of which there are several species 
mostly inhabiting the central plains, are rodents found 
only in North America. They all live underground, 
making extensive galleries and feeding chiefly on bulbous 
roots. The mice and rats constitute a large family of 
which the house-mice and rats, the various field-mice, the 
wood-rat (Neotoma pennsylvanica) and the muskrat [Fiber 
zibethicus) are familiar representatives. The common 



BRANCH CHORD AT A: CLASS MAMMALIA 39 I 

brown rat {Mus decumanns) was introduced into this 
country from Europe about 1775, and has now nearly 
wholly supplanted the black rat (M. rattus), also a 
European species, introduced about 1544. The beaver 
{Castor canadensis) is the largest rodent. It seems to be 
doomed to extermination through the relentless hunting 
of it for its fur. The woodchuck or ground-hog (Arctomys 
monax) is another familiar rodent larger than most mem- 
bers of the order. The chipmunks and ground-squirrrels 
are commonly known rodents found all over the country. 
They are the terrestrial members of the squirrel family, 
the best known arboreal members of which are the red 
squirrel (Scinrus hudsonicus), the fox-squirrrel (5. ludo- 
vicianiis), and the gray or black squirrel (5. carolinensis). 
The little flying squirrel {Sciiiroptcrus volans) is abundant 
in the Eastern States. 

The shrews and moles (Insectivora). — The shrews 
and moles are all small carnivorous animals, which, 
because oftheir size, confine their attacks chiefly to insects. 
The shrews are small and mouse -like; certain kinds of 
them lead a semi-aquatic life. There are nearly a score 
of species in North America. Of the moles, of which there 
are but few species, the common mole (Sea/ops aqnaticus) 
is well known, while the star-nosed mole (Condylura 
crista! d) is recognizable by the peculiar rosette of about 
twenty cartilaginous rays at the tip of its snout. Moles 
live underground and have the fore feet wide and shovel- 
like for digging. The European hedgehogs are members 
of this order. 

The bats (Chiroptera). — The bats (fig. 153), order Chi- 
roptera, differ from all other mammals in having the fore 
limbs modified for flight by the elongation of the forearms 
and especially of four of the fingers, all of which are con- 
nected by a thin leathery membrane which includes also 
the hind feet and usually the tail. Bats are chiefly nog- 



39 2 



ELEMENTARY ZOOLOGY 



turnal, hanging head downward by their hind claws in 
caves, hollow trees, or dark rooms through the day. They 
feed chiefly on insects, although some foreign kinds live 
on fruits. There are a dozen or more species of bats in 
North America, the most abundant kinds in the Eastern 
States being the little brown bat (Myotis subulatus), about 
three inches long with small fox-like face, high slender 
ears, and a uniform dull olive-brown color, and the red 
bat {Lasiurus borcalis), nearly four inches long, covered 




Fig. 153. — The hoary bat, Lasiurus cinereus. 

by J. O. Snyder.) 



(Photograph from life 



with long, silky, reddish-brown fur, mostly white at tips 
of the hairs. 

The dolphins, porpoises, and whales (Cete).— The 

dolphins, porpoises, and whales (Cete) compose an order 
of more or less fish-like aquatic mammals, among which 



BRANCH CHORDA TA : CLASS MAMMALIA 393 

are the largest of living animals. In all the posterior limbs 
are wanting, and the fore limbs are developed as broad 
flattened paddles without distinct fingers or nails. The 
tail ends in a broad horizontal fin or paddle. The Cete 
are all predaceous, fish, pelagic crustaceans, and especially 
squids and cuttlefishes forming their principal food. Most 
of the species are gregarious, the individuals swimming 
together in " schools.' The dolphins and porpoises 
compose a family (Delphinidae) including the smaller 
and many of the most active and voracious of the Cete. 
The whales compose two families, the sperm-whales 
(Physeterida^) with numerous teeth (in the lower jaw 
only) and the whalebone whales (Balaenidae) without 
teeth, their place being taken in the upper jaw by an array 
of parallel plates with fringed edges known as "whale- 
bone.' The great sperm-whales or cachalots (Physeter 
macrocephalus) found in southern oceans reach a length 
(males) of eighty feet, of which the head forms nearly 
one-third. Of the whalebone whales, the sulphur-bottom 
(Balcznoptera su If urea) of the Pacific Ocean, reaching a 
length of nearly one hundred feet, is the largest, and hence 
the largest of all living animals. The common large 
whale of the Eastern coast and North Atlantic is the right 
whale {Balcena glacialis) ; a near relative is the great 
bowhead (B. mysticetus) of the Arctic seas, the most 
valuable of all whales to man. Whales are hunted for 
their whalebone and the oil yielded by their fat or blubber. 
The story of whale-fishing is an extremely interesting 
one, the great size and strength of the "game " making 
the "fishing " a hazardous business. 

The hoofed mammals (Ungulata). — The order Ungu- 
lata includes some of the most familiar mammal forms. 
Most of the domestic animals, as the horse, cow, hog, 
sheep, and goat, belong to this order, as well as the 
familiar deer, antelope, and buffalo of our own land and 



94 



ELEMENTARY ZOOLOGY 



the elephant, rhinoceros, hippopotamus, giraffe, camel, 
zebra, etc., familiar in zoological gardens and menageries. 
The order is a large one, its members being characterized 
by the presence of from one to four hooves, which are the 
enlarged and thickened claws of the toes. The Ungulates 
are all herbivorous, and have their molar teeth fitted for 




Fig. 154. — Male elk or wapiti, Cervus canadensis. (Photograph by E. 
Willis from specimen mounted by Prof. L. L. Dyche, University of 

Kansas.) 

grinding, the canines being absent or small. The order 
is divided into the Perissodactyla or odd-toed forms, like 
the horse, zebra, tapir, and rhinocerus, and the Artio- 
dactyla or even-toed forms, like the oxen, sheep, deer, 



BRANCH CHORD AT A: CLASS MAMMALIA 



395 



camels, pigs, and hippopotami. The Artiodactyls com- 
prise two groups, the Ruminants and Non-ruminants. 
All of the native Ungulata of our Northern States belong 
to the Ruminants, so called because of their habit of 




chewing a cud. A ruminant first presses its food into a 
ball, swallows it into a particular one of the divisions of 
its four-chambered stomach, and later regurgitates it into 



$9 6 ELEMENTARY ZOOLOGY 

the mouth, thoroughly masticates it, and swallows it 
again, but into another stomach-chamber. From this it 
passes through the other two into the intestine. 

The deer family (Cervidae) comprises the familiar Vir- 
ginia or red deer {Odoccileus americanns) of the Eastern 
and Central States and the white-tailed, black-tailed, and 
mule deers of the West, the great-antlered elk or wapiti 
{Cervns canadensis) (fig. 154), the great moose {Alee 
amerieand) (fig. 152), largest of the deer family, and the 
American reindeer or caribou (Rangifer earibon). All 
species of the Cervidae have solid horns, more or less 
branched, which are shed annually. Only the males (ex- 
cept with the reindeer) have horns. The antelope (Anti- 
locapra amerieand) (fig. 155) common on the Western 
plains also sheds its horns, which, however, are not solid 
and do not break off at the base as in the deer, but are 
composed of an inner bony core and an outer horny 
sheath, the outer sheath only being shed. The family 
Bovidae includes the once abundant buffalo or bison {Bison 
bison) (frontispiece), the big-horn or Rocky Mountain 
sheep (Ovis canadensis) (fig. 151), and the strange pure- 
white Rocky Mountain goat (Oreamnos montanus). The 
buffalo was once abundant on the Western plains, travelling 
in enormous herds. But so relentlessly has this fine animal 
been hunted for its skin and flesh that it is now practically 
exterminated (fig. 156). A small herd is still to be found 
in Yellowstone Park, and a few individuals live in parks 
and zoological gardens. In all of the Bovidae the horns 
are simple, hollow, and permanent, each enclosing a 
bony core. 

The carnivorous mammals (Ferae). — The order Ferae 
includes all those mammals usually called the carnivora, 
such as the lions, tigers, cats, wolves, dogs, bears, 
panthers, foxes, weasels, seals, etc. All of them feed 
chiefly on animal substance and are predatory, pursuing 



BRANCH CHORD AT A: CLASS MAMMALIA 



197 



and killing their prey. They are mostly fur-covered and 
many are hunted for their skin. They have never less 
than four toes, which are provided with strong claws that 
are frequently more or less retractile. The canine teeth 
are usually large, curved, and pointed. 

While most of the Ferae live on land, some are strictly 
aquatic. The true seals, fur-seals, sea-lions, and walruses 
comprise the aquatic forms, all being inhabitants of the 
ocean. The true seals, of which the common harbor seal 
{Plioca vitulina) is our most familiar representative, have 




Fig. 156. — A buffalo, Bison bison, killed for its skin and tongue, on the 
plains of Western Kansas thirty years ago. (Photograph by J. Lee 
Knight. ) 

the limbs so thoroughly modified for swimming that they 
are useless on land. The fur-seals, sea-lions, and walruses 
use the hind legs to scramble about on the rocks or 



39 § ELEMENTARY ZOOLOGY 

beaches of the shore. The fur-seals (fig. 157) live gre- 
gariously in great rookeries on the Pribilof or F'ur Seal 
Islands, and the Commander Islands in Bering Sea. 

The bears are represented in our county by the wide- 
spread brown, black, or cinnamon bear (Ursus americantis) 
and the huge grizzly bear ( U. horribilis) of the West. The 
great polar bear {Thalarctos maritimus) lives in arctic 
regions. The otters, skunks, badgers, wolverines, sables, 
minks, and weasels compose the family Mustelidae, which 
includes most of the valuable fur-bearing animals. Some 
of the members of this family lead a semi-aquatic or even 
strictly aquatic life and have webbed feet. The wolves, 
foxes, and dogs belong to the family Canidae. The coyote 
[Cants latrans), the gray wolf (C. niibilns), and the red 
fox [Vulpes pennsylvanicns) are the most familiar repre- 
sentatives of this family, in addition to the dog (C. favii- 
liaris), which is closely allied to the wolf. "Most 
carnivorous of the carnivora, formed to devour, with every 
offensive weapon specialized to its utmost, the Felidae, 
whether large or small, are, relatively to their size, the 
fiercest, strongest, and most terrible of beasts.' The 
Felidae or cat family includes the lions, tigers, hyenas, 
leopards, jaguars, panthers, wildcats, and lynxes. In this 
country the most formidable of the Felidae is the American 
panther or puma (Felis concolor). It reaches a length 
from nose to root of tail of over four feet. Its tail is 
long. The wildcat {Lynx rnfits) is much smaller and 
has a short tail. 

The man-like mammals (Primates). — The Primates, 
the highest order of mammals, includes the lemurs, 
monkeys, baboons, ape-s, and men. Man {Homo sapiens) 
is the only native representative of this order in our 
country. All the races and kinds of men known, although 
really showing much variety in appearance and body 
structure, are commonly included in one species. The 



BRANCH CHORD AT A: CLASS MAMMALIA 



399 




+3 P 
X g 

r- O 









c2s 



U 

J* 
Q 

O 









g 



4^0 



ELEMENTARY ZOOLOGY 



chief structural characteristics which distinguish man from 
the other members of this order are the great development 
of his brain and the non-opposabihty of his great toe. 
Despite the similarity in general structure between him 




Fig. 158. — " Bob Jordan," a monkey of the genus Cercopithecus. 
(Photograph from life by D. S. Jordan.) 

and the anthropoid apes of the Old World, in particular 
the chimpanzee and orang-outang, the disparity in size of 
brain is enormous. 

The lowest Primates are the lemurs found in Madagas- 
car, in which island they include about one-half of all 
the mammalian species found there. The brain is much 



BRANCH CHORD AT A: CLASS MAMMALIA 401 

less developed in the lemurs than in any of the other 
monkeys. The monkeys and apes may be divided into 
two groups, the lower, platyrrhine monkeys, found in the 
New World, and the higher, catarrhine forms, limited to 
the Old World. The platyrrhine monkeys have wide noses 
in which the nostrils are separated by a broad septum and 
with the openings directed laterally. These monkeys are 
mostly smaller and weaker than the Old World forms and 
are always long-tailed, the tail being frequently prehen- 
sile. They include the howling, squirrel, spider, and 
capuchin monkeys common in the forests of tropical South 
America. The catarrhine monkeys have the nose-septum 
narrow and the openings of the nostrils directed forwards, 
and the tail is wanting in numerous members of the group. 
They include the baboons, gorillas, orang-outangs, and 
chimpanzees. These apes have a dentition approaching 
that of man, and in all ways are the animals which most 
nearly resemble man in physical character. 



PART III 
ANIMAL ECOLOGY 

CHAPTER XXIX 

THE STRUGGLE FOR EXISTENCE, ADAPTA- 
TION, AND SPECIES-FORMING 

Technical Note. — Multiplication, or increase by geometric 
ratio, among animals can be illustrated by noting the many eggs 
laid by a single female moth or beetle or fly or mosquito or any 
other common insect (or almost any other non-mammalian animal). 
The production of many live young by each female rose aphid can 
be readily seen ; the number of young in a litter of kittens or pups 
or rabbits is a good illustration. From this geometric increase it is 
obvious that there must be a great crowding of animals and a strug- 
gle among them for existence. This struggle and the downfall of 
the many and success of the victorious few 7 can be observed by 
rearing in a small jar of water all the young of a single brood of 
water-tigers (larva of Dyticus) or other aquatic predaceous insect. 
The strongest young will live by killing and eating the weaker of 
their own kind. In a spider's egg-sac the young after hatching do 
not immediately leave the sac, but remain in it for several days. 
During this time they live on each other, the strongest feeding on 
the weaker. Thus out of many spiderlings hatched in each sac com- 
paratively few issue. This can be readily observed. Open several 
egg-sacs and count the eggs in them. Let the spiderlings hatch 
and i-ssue from some other egg-sacs belonging to the same species 
of spider. The number of issuing spiderlings will always be much 
less than that of the eggs. The actual working of natural selection 
and the forming of new species can of course be seen only in re- 
sults, and not in process. The great variety of adaptation, the fit- 
ness of adaptive structures, can be readily illustrated among the 
commonest animals. Animals showing certain striking and unusual 
adaptations will perhaps make the matter more obvious. To all 
teachers will occur numerous opportunities of illustrating, by refer- 

403 



404 ELEMENTARY ZOOLOGY 

ence to actual processes or to obvious results, the principles of this 
chapter. 

The multiplication and crowding of animals. — In the 

reproduction or multiplication of animals the production 
of young proceeds in geometric ratio, that is, it is truly a 
multiplication. Any species of animal, if its multiplica- 
tion proceeded unchecked, would sooner or later be 
sufficiently numerous to populate exclusively the whole 
world. The elephant is reckoned the slowest breeder of 
all known animals. It begins breeding when thirty years 
old and goes on breeding until ninety years old, bringing 
forth six young in the interval, and surviving until a 
hundred years old. Thus after about eight hundred years 
there would be, if all the individuals lived to their normal 
age limit, 19,000,000 elephants alive descended from the 
first pair. A few years more of unchecked multiplication 
of the elephant and every foot of land on the earth would 
be covered by them. But the rate of multiplication of 
other animals varies from a little to very much greater 
than that of the elephant. It has been shown that at the 
normal rate in increase in English sparrows, if none were 
to die save of old age, it would take but twenty years to 
give one sparrow to every square inch in the State of 
Indiana. The rate of increase of an animal, each pair 
producing ten pairs annually and each animal living ten 
years, is shown in the following table: 

Pairs alive at end of year. 

I I 
121 

14,641 

161,051 

25,937,424,600 

700,000,000,000,000,000,000 



r ears. 


Pairs produced. 


I 


IO 


2 


no 


3 


1,210 


4 


13,310 


5 


146,410 


10 




20 





THE STRUGGLE FOR EXISTENCE ^05 

Some animals produce vast numbers of eggs or young; 
for example, the herring, 20,000; a certain eel, several 
millions; and the oyster from 500,000 to 16,000,000. 
Supposing we start with one oyster and let it produce one 
million of eggs. Let each egg produce an oyster which 
in turn produces * one million of eggs, and let these go 
on increasing at the same rate. In the second generation 
there would be one million million of oysters, and in the 
fourth, i.e. the great great grandchildren of the first oyster, 
there would be one million million million million of 
oysters. The shells of these oysters would just about 
make a mass the size of the earth. 

But it is obvious that all the new individuals of any 
animal produced do not live their normal duration of life. 
All animals produce far more young than can survive. 
As a matter of fact, which we may verify by observation, 
the number of individuals of animals in a state of nature is, 
in general, about stationary. There are about as many 
squirrels in the forest one year as another, about as many 
butterflies in the field, about as many frogs in the pond. 
Some species increase in numbers, as for example, the 
rabbit in Australia, which was introduced there in i860 
and in fifteen years had become so abundant as to be a 
great pest. Other species decrease, as the buffaloes, which 
once roamed our great plains in enormous herds and are 
now represented by a total of a few hundred individuals, 
and the passenger-pigeon, whose migrating flocks ten years 
ago darkened the air for hours in parts of the Mississippi 
valley, where now it is a rare bird. But the hand of man 
is the agent which has helped to increase or to check the 
multiplication of these animals. In nature such quick 
chanees rarelv occur. 



* Oysters are hermaphroditic, each individual producing both sperm- and 
egg-cells. 



406 ELEMENTARY ZOOLOGY 

The struggle for existence. — The numbers of animals 
are stationary because of the tremendous mortality occa- 
sioned by the constant preying on eggs and young and 
adults by other animals, because of strenuous and destruc- 
tive climatic and meteorological conditions, and because 
there is not space and food for all born, not even, indeed, 
for all of a single species, let alone all of the hundreds of 
thousands of species which now inhabit the earth. There 
is thus constantly going on among animals a fearful 
struggle for existence. In the case of any individual this 
struggle is threefold: (i) with the other individuals of his 
own species for food and space; (2) with the individuals 
of other species, which prey on him, or serve as his prey, 
or for food and space; and (3) finally with the conditions 
of life, as with the cold of winter, the heat of summer, or 
drouth and flood. Sometimes one of these struggles is 
the severer, sometimes another. With the communal 
animals the struggle among individuals is lessened — they 
help each other ; but when the struggle with the condi- 
tions of life are easiest, as in the tropics or in the ocean, 
the struggle among individuals becomes intensified. Each 
strives to feed itself, to save its own life, to produce and 
safeguard its young. But in spite of all their efforts only 
a few individuals out of the hosts produced live to 
maturity. The great majority are destroyed in the egg 
or in adolescence. 

Variation and natural selection. — What individuals 
survive of the many which are born ? Those best fitted 
for life ; those which are a little stronger, a little swifter, 
a little hardier, a little less readily preceived by their 
enemies, than the others. They are the winners in the 
struggle for existence; they are the survivors. And this 
survival of the fittest, as it is called, is practically a process 
of selection by Nature. Nature selects the fittest to live 
and to perpetuate the species. Their progeny again 



THE STRUGGLE FOR EXISTENCE 407 

undergo the struggle and the selecting process, and again 
the fittest live. And so on until adjustment or harmoniz- 
ing of animals' bodies and habits with the conditions of 
life, with their environment, comes to be extremely fine 
and nearly perfect. 

It is evident, of course, that such a natural selection or 
survival of the fittest and consequent adaptation to en- 
vironment presupposes differences among the individuals 
of a species. And this is an observed fact. No two 
individuals, although of the same brood, are exactly alike 
at birth ; there always exist slight variations in structure 
and performance of functions. And these slight variations 
are the differences which determine the fate of the indi- 
vidual. One individual is a little larger or stronger or 
swifter or hardier than its mates. The existence of this" 
variation we know from our observation of the young 
kittens or puppies of a brood. So it is with all animals. 
Thus natural selection depends upon two factors, namely, 
the excess in the production of new individuals and the 
consequent struggle for existence among them, and the 
existence of variations which give certain individuals 
slight advantages in this struggle. 

Adaptation and adjustment to surroundings. — The 
action of natural selection obviously must, and does, 
result in a fine adaptation and adjustment of the structure 
and habits of animals to their surroundings. If a certain 
species or group of individuals cannot adapt itself to its 
environment, it will be crowded out by others that can. 
A slight advantageous variation comes in time by the 
continuously selective process to be a well-developed 
adaptation. 

The diverse forms and habits possessed by animals are 
chiefly adaptations to their special conditions of life. 
The talons and beak of the eagle, the fishing-pouch of the 
pelican, the piercing chisel-like bill of the woodpecker, 



408 ELEMENTARY ZOOLOGY 

and the sensitive probing-bill of the snipe are adaptations 
connected with the special feeding habits of these birds. 
The quills of the porcupine, the poison-fangs of the rattle- 
snake, the sting of the yellow-jacket, and the antlers of 
the deer are adaptations for self-defence. The fins and 
gills of fishes, the shovel-like fore feet of the mole, the 
wings of birds and insects and bats, the toe-pads of the 
tree-toad, the leaping-legs of the grasshopper, all these 
are adaptations concerned with the. special life-surround- 
ings of these animals. 

Adaptations may relate to habits and behavior as well 
as to structure. Plainly adaptive are such habits as the 
migration of birds and some other animals, most of the 
habits connected with food-getting, and especially striking 
and interesting those connected with the production and 
care of the young, including nest-making and home- 
building. 

Species-forming. — It is evident that through the cumu- 
lative action of natural selection, animals of a structural 
type considerably (even unlimitedly) different from any 
original type may in time be produced by the gradual 
modification of the original type under new conditions. 
If, for example, a few individuals of a mainland species 
should come to be thrown as waifs of wave and storm 
upon an island, and if these should be able to maintain 
themselves there and produce young, increasing so as to 
occupy the new territory, there would be produced in time 
a new type of individual conforming or adapted to the 
conditions obtaining in the island, these conditions being, 
of course, almost certainly different from those of the 
mainland. Thus as an offshoot or derivation from the 
original type still existing on the mainland we should 
have the new island-inhabiting type. Now when these 
island individuals come to differ so much, structurally and 
physiologically, from the mainland type that they cannot. 



THE STRUGGLE FOR EXISTENCE 400 

even if opportunity offers, successfully mate or interbreed 
with mainland individuals the island type constitutes a 
new species. That is, our distinction between species 
rests not only on structural differences, but on the impossi- 
bility of interbreeding (at least for the production of fertile 
young). Such a combination of the action of natural 
selection and the condition of isolation (as illustrated by 
the case of island animals), is probably the most potent 
factor in the production of new species of animals (and 
plants). 

For accounts of the struggle for existence, variations, 
adaptations, natural selection and species-forming see 
Darwin's ' 4 Origin of Species," Wallace's " Island Life," 
and Romanes' tk Darwin and After Darwin," I. 

Artificial selection. — When a selection among the 
individuals of a species, that is, the choosing and preserv- 
ing of individuals which show a certain trait or traits and 
the destroying of those individuals not possessing this 
trait, is done by man, it is called artificial selection. To 
artificial selection we chiefly owe all the many races or 
varieties of our domesticated animals and plants. For 
example, from the ancestral jungle fowl have been devel- 
oped by artificial selection (and by cross-breeding) all our 
kinds of domestic fowl, as Brahmas, black Spanish, 
bantams, game-cocks, etc. ; from the wild rock-dove have 
been developed our various fancy pigeons, as carriers, 
pouters, fantails, etc. 

For an account of artificial selection see Darwin's 
44 Plants and Animals under Domestication," and 
Romanes' " Darwin and After Darwin," I. 



CHAPTER XXX 

SOCIAL AND COMMUNAL LIFE, COMMEN- 
SALISM AND PARASITISM 

Social life and gregariousness. — Technical note.— 

Students should refer to examples of gregariousness from their own 
observations of animals. The roosting together of crows and of black- 
birds ; the gathering of swallows preparatory to migration ; the 
flocking of geese and ducks, with leaders, in their migratory flights, 
all can be readily observed. From observation or general reading 
students will be more or less familiar with prairie-dog villages, 
beaver-dams and marshes, the one-time great herds of bison, etc. 

The struggle for existence is always operative ; but in 

some cases one or more phases of it may be ameliorated. 

For example, the amelioration of the struggle among 

individuals of one species obtains in a lesser or greater 

degree in the case of those animals which exhibit a social 

life, of which mutual aid and mutual dependence are the 

basis. The honey-bee and the ants are familiar examples 

of animals which show a high degree of social life. They 

live, indeed, a truly communal life, where the fate of the 

individual is bound up in the fate of the community. 

But there are many animals which show a much lower 

degree of mutual aid and a far less coherent society. 

The simplest form of social life exists among those animals 

in which many individuals of one species keep together, 

forming a great band or herd. In this case there is not 

nearly so much mutual aid or mutual dependence as in 

that of the honey-bee, and the safety of the individual is 

\ot wholly bound up in the fate of the herd. Such 

410 



SOCIAL AND COMMUNAL LIFE 41 1 

animals are said to be gregarious in habit, and this gre- 
gariousness is undoubtedly advantageous to the individuals 
of the band. The great herds of reindeer in the North, 
and of the bison or buffalo which once ranged over the 
Western American plains are examples of a gregarious- 
ness in which mutual protection from enemies, like wolves^ 
seems to be the principal advantage gained. The bands 
of wolves which hunted the buffalo show the advantage 
of mutual help in aggression as well as in protection. 
Prairie-dogs live in great villages or communities which 
spread over many acres. By shrill cries they tell each 
other of the approach of enemies, and they seem to visit 
each other and to enjoy each other's society a great deal, 
although that they are thus afforded much actual active 
help is not apparent. The beavers furnish a well-known 
and very interesting example of mutual help ; they exhibit 
a communal life although a simple one. They live in 
villages or communities, all helping to build the dam 
across the stream which is necessary to form the marsh 
or pool in which the nests or houses are built. 

Communal life. — Technical Note. — See technical notes, 
pp. 212 et seq^ for directions for work in connection with the study 
of the communal life of ants, bees, and wasps. 

When many individuals of a species live together in a 
community in which the different kinds of work are divided 
more or less distinctly among the different members and 
where each individual works primarily for the whole and 
not for himself; where there is, in other words, a thorough 
mutual help and mutual dependence among the members 
of the community accompanied by a division of labor, the 
life of the species is truly communal. Those animals 
which show the most elaborate and specialized communal 
life are the termites or white ants, the social bees and 
wasps, and the true ants. Of these the ants and honey- 



4i2 ELEMENTARY ZOOLOGY 

bees stand first. As already explained (see pp. 220 et seq), 
there are among these communal insects several different 
kinds of individuals in each species. With most animals 
there are two kinds only, males and females, which may 
or may not show differences in color, form, etc., so that 
they are readily distinguishable. Among all the com- 
munal insects, however, there are always three kinds of 
individuals, males, females, and workers, these last being 
infertile individuals. With the social wasps and social 
bees the workers are all infertile females and are smaller 
than the fertile forms ; with the termites there are 
besides the fertile males and females, which are winged, 
workers which are wingless, and also peculiar wingless 
individuals called soldiers which have very large jaws and 
whose business it is to fight off attacking enemies of 
the community. Among the ants the workers are also 
wingless, while the males and females are winged. The 
worker ants in many species are of two kinds, so-called 
worker majors and worker minors, differing markedly in 
size. All the ant workers are good soldiers, but with 
some the fighting is done almost wholly by certain 
especially large-headed and large-jawed ones which may 
be called soldier-workers. 

Thus among all strictly communal animals there is a 
specialization or differentiation of individuals accompany- 
ing the division of labor. Special individuals have a 
certain part of the work of the community to do, and they 
are specially modified in structure to do this work. This 
structural modification may make them incapable of per- 
forming certain other labor or work which is necessary 
for their living and which must be done for them, therefore, 
by others. Thus the mutual interdependence of the in- 
dividuals composing a colony is very real. The worker 
honey-bees cannot perpetuate the species; honey-bees 
would die out were it not for the males and females. But 



SOCIAL AND COMMUNAL LIFE 4*3 

the males and females have given up the functions of food- 
getting and of caring for their young ; did not the workers 
do these things for them, the community would die out 
quite as soon. 

The advantages of communal or social life, of co-opera- 
tion and mutual aid are real. Those animals that have 
adopted such a life are among the most successful of all 
in the struggle for existence. The termite worker is 
one of the most defenseless and for those animals that 
prey on insects one of the most toothsome insects, and 
yet the termite is one of the most abundant and success- 
fully living insect kinds in all the tropics. Ants are 
everywhere and are everywhere successful. The honey- 
bee is a popular type of successful life. The artificial 
protection afforded it by man may aid it in its struggle 
for existence, but it gains this protection because of certain 
features of its communal life, and in nature the honey-bee 
takes care of itself well. Co-operation and mutual aid 
are among the most important factors which help in the 
struggle for existence. 

Commensalism. — Technical Note. — Examine ants' nests 
to find myrmecophilous insects. If on the seashore search for hermit- 
crabs with sea-anemones on shell. If inland, try to have some pre- 
served specimens showing the crabs and sea-anemones. 

The phases of living together and mutual help just dis- 
cussed concerned in each instance a single species of 
animal. All the members of a pack of wolves or of a 
honey-bee ^community belong to a single species. But 
there are numerous instances known of the mutual lv 
advantageous association of individuals of two different 
species. Such an association is called commensalism or 
symbiosis. 

The hermit-crabs live, as has been learned (p. 154), in 
the shells of molluscs, most of the body of the crab being 
concealed within the shell, only the head and the grasping 



414 ELEMENTARY ZOOLOGY 

and walking legs protruding. In some species of hermit- 
crabs there is always to be found on the shell near the 
opening a sea-anemone. "This sea-anemone is carried 
from place to place by the crab, and in this way is much 
aided in obtaining food. On the other hand, the crab is 
protected from its enemies by the well-armed and dan- 
gerous tentacles of its companion. On the tentacles there 
are many thousand long slender stinging threads, and the 
fish that would eat the hermit-crab must first deal with 
the stinging anemone.' If the sea-anemone be torn 
away from the shell the crab will wander about seeking 
another anemone. When he finds one, he struggles to 
loosen it from the rock to which it is attached, and does 
not rest until he has torn it loose and placed it on his 
shell. 

In the case of the hermit-crab and the sea-anemone 
there is no doubt of the mutual advantage derived from 
their communal life. But this mutual advantage is not 
so obvious in some cases of commensalism, where indeed 
most or all of the advantage often seems to lie with one 
of the animals, while the other derives little or none, but 
on the other hand suffers no injury. For example, 
44 small fish of the genus Nomeus may often be found 
accompanying the beautiful Portuguese man-of-war 
(Physalid) as it sails slowly about on the ocean's surface. 
These little fish lurk underneath the float among the 
various hanging thread-like parts of the man-of-war which 
are provided with stinging cells. They are protected 
from their enemies by their proximity to these stinging 
threads, but of what advantage to the man-of-war their 
presence is is not understood.' Similarly in the nests of 
the various species of ants and termites many different 
kinds of other insects have been found. " Some of these 
are harmful to their hosts, in that they feed on the food- 
stores gathered by the industrious and provident ant, but 



SOCIAL AND COMMUNAL LIFE 415 

others appear to feed only on refuse or useless substances 
in the nest. Some may be of help to their hosts by 
acting as scavengers. Over one thousand species of these 
myrmecophilous (ant-loving) and termitophilous (termite- 
loving) insects have been recorded by collectors as living 
habitually in the nests of ants and termites. ' 

Parasitism. — Technical Note. — As examples of temporary 
external parasites find and examine fleas and ticks on dogs and cats, 
red mites on house-flies and grasshoppers (at the bases of the 
wings), etc. As examples of permanent external parasites find 
bird-lice on pigeons or domestic fowls or on other birds. Note the 
absence of wings and the peculiarly modified body shape of these 
parasites. Examine a bird-louse under the microscope ; note the ab- 
sence of compound eyes (it has simple eyes) and absence of wings; 
note bits of feathers, its food, in stomach, showing through the 
body. Find, as examples of internal parasites, intestinal worms or 
flukes. Examine trichinized pork to see Trichina in muscles. Ex- 
amine preserved specimens of tapeworms. Collect pupae of some 
common butterfly or moth and keep them in the schoolroom until 
either the butterflies or ichneumon flies issue. Some will surely be 
parasitized, and yield ichneumon flies (parasites) instead of a butter- 
fly. As examples of degeneration by quiescence examine barnacles 
(found on outer rocks of seashore at low tide ; easily obtained as 
preserved specimens by inland schools) and the females of scale- 
insects. These insects may be found on oleanders (the black scale, 
Lecanium olece) or fruit-trees (the San Jose scale, Aspidiotus per- 
niciosus). Note the great degeneration of the adult female of the 
San Jose scale ; it has no eyes, antennae, wings, or legs. The 
young may be found crawling about at certain times of the year ; 
they have eyes, antennae, and legs. 

In addition to the various ways of living together among 
animals, already described, namely, the social and com- 
munal life of individuals of a single species and the com- 
mensal and symbiotic life of individuals of different species, 
there is another and very common kind of association 
among animals. This is the association of parasite and 
host ; the association between two sorts of animals w r hereby 
one, the parasite, lives on or in the other, the host, and at 
the expense of the host. In this association the parasite 
gains advantages great or small, sometimes even obtain- 
ing all the necessities of life, while the host gains nothing, 



4i 6 ELEMENTARY ZOOLOGY 

but suffers corresponding disadvantage, often even the loss 
of life itself. Parasitism is a phenomenon common in 
all the large groups of animals, though the parasites 
themselves are mostly invertebrates. There are parasitic 
Protozoa, worms, crustaceans, insects, and molluscs, and 
a few vertebrates. 

Some parasites, like the fleas and lice, live on the sur- 
face of the body of the host. These are called external 
parasites. Others, as the tapeworms, live exclusively 
inside the body; such are called internal parasites. 
Again, some, as the bird-lice, which are external parasites 
feeding on the feathers of birds, spend their whole life- 
time on the host; they are called permanent parasites. 
Others, as a flea, which leaps on or off its host as caprice 
directs, or like certain parasites which as young live free 
and active lives, finally attaching themselves to some host 
and remaining fixed there for the rest of their lives, are 
called temporary parasites. Such a grouping is purely 
arbitrary and exists simply for the sake of convenience. 
It is not rigid, nor does it class parasites in their proper 
natural groups. 

When various parasites are examined it will be noted 
that practically in all cases the body of a parasite is 
simpler in structure than the body of other animals closely 
related to it; that is, species which live parasitically, 
obtaining their food from and being carried about by a 
host, have simpler bodies than related forms that live free 
active lives, competing for food with other animals about 
them. This simplicity is not primitive, but results from 
the loss or atrophy of the structures which the special 
mode of life of the parasite renders useless. Many para- 
sites are attached firmly by hooks or suckers to their host, 
and do not move about independently of it. They have 
no need of the power of locomotion, and accordingly are 
usually without wings, legs, or other locomotory organs. 



SOCIAL AND COMMUNAL LIFE 417 

Because they have no need of locomotion they have no 
need of organs of orientation, those special sense organs 
like the eyes, ears, and feelers which serve to guide and 
direct the moving animal ; and most fixed parasites will 
be found to have no eyes, or any of those organs acces- 
sory to locomotion, and which serve for the detection of 
food or of enemies. Because these important organs, 
which depend for their successful activity on a well-organ- 
ized nervous system, are lacking, the nervous system of 
parasites is usually very simple. Again, because the 
parasite usually feeds on the already digested food or the 
blood of its host, most parasites have a very simple ali- 
mentary canal, or even none at all. Finally, as the fixed 
parasite leads a wholly sedentary and inactive life, the 
breaking down and rebuilding of tissue in its body goes 
on very slowly and in minimum degree, so that there is 
little need of highly developed respiratory and circulatory 
systems; and most fixed and internal parasites have these 
systems of organs decidedly simplified. Altogether the 
body of a fixed permanent parasite is so simplified and so 
wanting in all those special structures which characterize 
the active, complex animals that it often presents a very 
different appearance from those forms with which we know 
it to be nearly related. This, simplicity due to loss or 
reduction of parts is called degeneration. Such simplicity 
of body-structure due to degeneration is, however, essen- 
tially different in its origin from the simplicity of the lower 
simpler animals. In them the simplicity of body is prim- 
itive ; they are generalized animals ; the simplicity of 
degeneration is acquired; it is really an adaptation, or 
specialization. 

An excellent example of body degeneration due to the 
adoption of a parasitic habit is that of Sacculina (fig. 159), 
a crustacean parasitic on other crustaceans, namely, crabs. 
The young Sacculina is an active, free-swimming larva 



4i8 



ELEMENTARY ZOOLOGY 



essentially like a young prawn or crab. After a short 
period of independent existence it attaches itself to the 
abdomen of a crab, and lives as a parasite. It completes 
its development under the influence of this parasitic life, 
and when adult bears absolutely no resemblance to such 




Fig. 159. — Sacculina* a parasitic crustacean; A, attached to a crab, the 
root-like processes of the parasite penetrating the body of the host; B. 
the active larval condition; C, the adult removed from its host. (After 
Haeckel.) 

a typical crustacean as a crab or crayfish. Its body ex- 
ternal to the host crab is simply a pulsating tumor-like 
sac, with no mouth-parts, no legs, and internally hardly 
any well-developed organs except those of reproduction. 
Degeneration here is carried very far. 



SOCIAL AND COMMUNAL LIFE 4*9 

Various parasites have been referred to in Part II under 
their proper branch and class. The worms include an 
unusually large number of them, such as the tape- 
worms, trichinae and other intestinal forms, ail of which 
live as internal parasites in the alimentary canal or in 
other organs of higher animals, especially the vertebrates. 
Many crustaceans are parasitic, usually living, like the 
fish-lice, as fixed external parasites on fishes, other crus- 
taceans, etc., but with a free and active larval stage. 
Among the insects, on the contrary, many of the parasitic 
forms ('as the ichneumon flies) are free and active in the 
adult stage, but live as internal grubs or maggots in the 
larval sta^e. The ichneumon flies ('of the order Hvmen- 
optera) are four-winged, slender-bodied insects which 
lay their eggs either on or in (by means of a sharp pierc- 
ing ovipositor) some caterpillar or beetle grub, into the 
body of which the voun? ^rub-like ichneumon larvae 
burrow on hatching. The parasites feed on the body- 
tissues of the host, not attacking, however, such organs 
as the heart or nervous system, which would produce the 
immediate death of the host. The caterpillar lives with 
the ichneumon grubs within it usually until nearly time 
for its pupation. Often, indeed, it pupates with the para- 
site still in its body. But it never comes to maturity. 
The larval ichneumons pupate either within the body of 
its host, or in a tiny silken cocoons outside of its body 
(fig. 1 60 1. From the cocoons the winged adult ichneu- 
mons issue ; and after mating the females find another 
caterpillar on whose body to lay their eggs. 

Degeneration can be produced by other causes than 
parasitism. It is evident that if for any other reason an 
animal should adopt an inactive fixed life it would degen- 
erate. The barnacles (see fig. 37) are excellent examples 
of degeneration through quiescence. The}' are crustaceans 
related most nearly to the crabs and shrimps. The 



420 



ELEMENTARY ZOOLOGY 



young barnacle just from the egg is a six-legged, free- 
swimming larva (nauplius) with a single eye, greatly like 
a young prawn or crab. It develops during its independ- 
ent life two compound eyes and two large antennae. But 

soon it attaches itself to some 
stone or shell, or pile or ship's 
bottom, giving up its power of 
locomotion, and its further de- 
velopment is a degeneration. It 
loses its compound eyes and an- 
tennae, and acquires a protecting 
shell. Its swimming feet become 
modified into grasping organs, 
and it loses most of its outward 
resemblance to the typical mem- 
bers of its class. The Tunicata 
or ascidians compose a whole 
group of animals which are fixed 
in their adult condition and have 
thus become degenerate. They 
have been likened to a "mere 
rooted bag with a double neck." 
In their young stage they are 
free-swimming, active, tadpole- 
like or fish -like larvae, possessing 
organs much like those of the 
adult simplest fish or fish-like 
animals. Their larval structure reveals, however, the 
relationships of the ascidians to the vertebrates, a rela- 
tionship which is not at all apparent in the degenerate 
adults. Certain insects live sedentary or fixed lives. All 
the members of one large family, the Coccidae, or scale- 
insects (figs. 62 and 63), have females which as adults are 
wingless and in some cases have no legs, eyes, or antennae, 
while the males are all winged and have legs and the 




Fig. 160. — Larva of a sphinx- 
moth, with cocoons of a para- 
sitic ichneumon fly. (From 
specimen. ) 



SOCIAL AND COMMUNAL LIFE 421 

special sense organs. The males lead a free active life, 
but the females have nearly or quite given up the power 
of locomotion, attaching themselves by means of their 
sucking beak to some plant, where they obtain a suffi- 
cient food-supply (plant-sap) and lay their eggs. In both 
males and females the larvae are little active crawling six- 
legged creatures with legs, eyes, and antennae. 

We are accustomed perhaps to think of degeneration 
as necessarily implying a disadvantage in life. It is true 
that a blind, footless, degenerate animal could not cope 
with the active, keen-sighted, highly organized non- 
degenerate in free competition. But free competition is 
exactly what the degenerate animal has nothing to do 
with. Certainly the Saccidina and the scale-insects live 
well ; they are admirably adapted to the kind of life they 
lead. A parasite enjoys certain obvious advantages in life, 
and even extreme degeneration is no drawback (except as 
we shall see later), but gives it a body which demands less 
food and care. As long as the host is successful in elud- 
ing its enemies and avoiding accident and injury the para- 
site is safe. Its life is easy as long as the host lives. 
But the disadvantages of parasitism and degeneration are 
nevertheless obvious. The fate of the parasite is bound 
up with the fate of the host. " When the enemy of the 
host crab prevails, the Saccidina goes down without a 
chance to struggle in its own defence. But far more im- 
portant than the disadvantage in such particular or indi- 
vidual cases is the fact that the parasite cannot adapt itself 
in any considerable degree to new conditions. It has 
become so modified, so specialized to adapt itself to the 
very special conditions under which it now lives, it has 
gone so far in giving up organs and functions, that if 
present conditions change and new ones come to exist 
the parasite cannot adapt itself to them. The independ- 
ent free-living animal holds itself, one may say, able and 



422 



ELEMENTARY ZOOLOGY 




SOCIAL AND COMMUNAL LIFE 4 2 3 

ready to adapt itself to any new conditions of life. The 
parasite has risked everything for the sake of a sure and 
easy life under the present existing conditions. Change 
of conditions means its extinction. 

For an elementary account of commensalism and para- 
sitism see Jordan and Kellogg's " Animal Life," pp. 172- 
200. The account here given is based on the author's 
previously written account in ''Animal Life.' See also 
Van Beneden's " Animal Parasites and Messmates." 



CHAPTER XXXI 
COLOR AND PROTECTIVE RESEMBLANCES 

Technical Note. — For an appreciation of the reality of pro- 
tective resemblances observations must be made in the field. Ex- 
amples are easily found. Locusts, katydids, green caterpillars, 
lizards, crouching rabbits, and brooding birds are readily observed 
instances of general protective resemblance. For examples of 
variable resemblance examine specimens of a single locust species 
taken from different localities ; the individuals of the various species 
of the genus Trimerotroftis show much variation to harmonize 
with their surroundings. Collect a number of larvae (caterpillars) of 
one of the swallow-tail butterflies (Paftilio), and when ready to 
pupate put them separately into pasteboard boxes lined inside with 
differently colored paper. The chrysalids will show in their colora- 
tion the influence of the different colors of the lining paper, their 
immediate environment. As examples of special protective resem- 
blance observe inch- or span-worms (larvae of Geometrid moths). 
The walking-stick is not uncommon ; many spiders that inhabit 
flower-cups show striking protective color patterns ; and the 
Graptas or comma-butterflies which resemble dead leaves may be 
examined. 

To illustrate warning colors, find, if possible, the larvae (cater- 
pillars) of the common milkweed or monarch butterfly (Anosia 
plexippus), and offer them to birds, at the same time offering other 
caterpillars, and note the results. For terrifying or threatening 
appearance find specimens of the large green tobacco- or tomato- 
worm (larva of the five-spotted sphinx-moth, Phlegethontius Caro- 
lina), or other sphingid larvae. 

The butterflies illustrating the striking example of mimicry, de- 
scribed on p. 432, can be found in most parts of the country. 
Syrphid and other flies which mimic bees and wasps can readily 
be found on flowers. 

Each student should search for himself for examples of pro- 
tective resemblance. 

Use of color. — The prevalence of color and the often- 
times striking and intricate coloration patterns of animals 

424 



COLOR AND PROTECTIVE RESEMBLANCES 425 

demand some explanation. As naturalists are accustomed 
to find the frequently bizarre and seemingly inexplicable 
shapes and general structure of animals readily explained 
by the principle of adaptation, that is, special modification 
of body-structure to fit special conditions of life, so they 
look to use as the chief explanation of color and markings. 
Some uses are obvious ; bright colors and striking patterns 
may serve to attract mates or to avail as recognition 
marks by which individuals of a kind may readily recog- 
nize each other. The white color of arctic animals prob- 
ably serves to help keep them warm by preventing 
radiation of heat from the body; on the other hand dark 
color may also help to keep animals warm by absorbing 
heat. "But by far the most widespread use of color is 
for another purpose, that of assisting the animal in escap- 
ing from its enemies or in capturing its prey. 

It is common knowledge that the young and old, too, 
of" many kinds of ground-inhabiting animals, when startled 
by an enemy will not run, but crouching close to the 
ground remain immovable, trusting to remain unper- 
ceived. But a blue or crimson rabbit, however still it 
might keep, w r ould be easily seen by its enemy and killed. 
Rabbits, however, which are good examples of animals 
having this habit of lying close, are neither blue nor green 
nor red, but are colored very much like the ground on 
which they crouch. This harmonious coloration is as 
necessary to the success of this habit as is the keeping 
still. A grasshopper flying or leaping in the air is con- 
spicuous ; when it alights how inconspicuous it is ! Unless 
one has followed it closely in its flight and has kept the 
eye fixed on it after alighting it is usually impossible to 
distinguish it from its surroundings. And this is greatly 
to the advantage of the grasshopper in its efforts to 
escape its enemies, that is, in its struggle for existence. 
On the other hand a green katydid would be very con- 



426 ELEMENTARY ZOOLOGY 

spicuous in a dusty road. But dusty roads are precisely 
where katydids do not rest. They alight among the 
green leaves of a tree or shrub. The animals that live in 
deserts are almost all obscurely mottled with gray and 
brownish and sand-color so as to harmonize in color with 
their habitual environment. The arctic hares and foxes 
and grouse which live in regions of perpetual snow are 
pure white instead of red or brown or gray like their 
cousins of temperate and warm regions. 

These cases of an animal's color and markings har- 
monizing with the usual environment are called instances 
of protective resemblance ; that is, they are resemblances 
for a purpose, that purpose being to render the animal in- 
distinguishable from its surroundings and thus to aid it in 
escaping its enemies. Such protective resemblances are 
obviously of great value to animals, and, like other 
advantageous modifications, have been produced by the 
action of natural selection. Those individuals of a species 
most conspicuous and hence most readily perceived by 
enemies are the first (under ordinary circumstances) to 
be captured and eaten. The less conspicuous live and 
produce young like themselves. Of these young the least 
conspicuous are again saved and so over and over again 
through thousands of generations until this natural select- 
ing of the protectively colored results in the production 
of the wonderfully specialized examples of resemblance 
to which attention is called in the following paragraphs. 

General, variable, and special protective resemblance. 
— In the brooks most fishes are dark olive or greenish 
above and white below. To the birds and other enemies 
which look down on them they are colored like the 
bottom. To their fish-enemies which look up from below 
they are like the white light above them in color and their 
forms are not clearly seen. The green tree-frogs and 
tree-snakes which live habitually among green foliage; 



COLOR AND PROTECTIVE RESEMBLANCES 



427 



the mottled gray and tawny lizards and birds and small 
mammals of the plains and deserts, and the white hares and 
foxes and owls and ptar- 
migan of the snowy arctic 
regions — all show a gener- 
al protective resemblance. 
Sometimes an animal 
changes color when its sur- 
roundings change. Certain 
hares and grouse of north- 
ern latitudes are white in 
winter when the snow 
covers all the ground, but 
in summer when much of 
the snow melts, revealing 
the brown and gray rocks 
and withered leaves, they 
put on a grayish and 
brownish coat of hair or 
feathers. A small insect 
called the toad-bug (Gal- 
guhts) lives abundantly on 
the banks of a pond on the 
campus of Stanford Uni- 
versity. The shores of 
this pond are covered in 
some places with bits of 
bluish rock, in others with 
bits of reddish rock, and 
in still others with sand. 
Specimens of the toad-bug 
collected from the blue 




Fig. 162, — The twig or walking-stick 
insect, Diapheroniera femorata. 
(From specimen.) 



rocks are bluish or leaden in color, those from the red rocks 
are reddish, and those from the sand are sand-colored. 
Changes of color to suit the surroundings can be quickly 



42 & ELEMENTARY ZOOLOGY 

made by some animals. The chameleons of the tropics 
change momentarily from green to brown, blackish, or 
golden. There is a little fish {Oligocottns snyderi) com- 
mon in the tide-pools of the Bay of Monterey in California 
whose color changes quickly to harmonize with the rocks 
it happens to rest above. Such changing coloration to 
suit the surroundings may be called variable protective 
resemblance. 

Very striking are those cases of protective resemblance 
in which the animal resembles in color and shape, some- 
times in extraordinary detail, some particular object or 
part of its usual environment. This may be called special 
protective resemblance. The larvae of the Geometrid 
moths called inch-worms or span-worms are twig-like in 
appearance, and have the habit, when disturbed, of stand- 
ing out stiffly from the twig or branch on w T hich they rest, 
so as to resemble in attitude as well as color and mark- 
ings a short or broken twig. To increase this simulation 
the body of the larva often has a few irregular spots or 
humps resembling the scars left by fallen leaves, and it 
also lacks the middle prop-legs of the body common to 
other lepidopterous larvae, which would tend to destroy 
the illusion so successfully carried out by it. The common 
twig-insect or walking-stick (fig. 162) with its wingless, 
greatly elongate, brown or greenish body and legs is when 
at rest quite indistinguishable from the twigs on which it 
lies. Another excellent example of special protective 
resemblance is furnished by the famous green-leaf insect 
{Phyllium) of the tropics, which has broad leaf-like wings 
and body of a bright green color with markings which 
imitate the leaf-veins, and small irregular yellowish spots 
which simulate decaying or stained or fungus-covered 
spots in the leaf. Most striking of all, however, is the 
large dead-leaf butterfly Kallima (fig. 163) of the East 
Indian region. The upper sides of the wing are dark 



COLOR AND PROTECTIVE RESEMBLANCES 4*9 




Fig. 163. — The dead-leaf butterfly, Kallima sp., a remarkable case of 
special protective resemblance. (From specimen.) 



43° ELEMENTARY ZOOLOGY 

with purplish and orange markings not at all resembling 
a dead leaf. But the butterflies when at rest hold their 
wings together over the back, so that only the under sides 
of them are exposed. These are exactly the color of a 
dry dead leaf with markings mimicking midrib and 
oblique veins, and, most remarkable of all, what are 
apparently two holes like those made in leaves by insects, 
but in the butterfly imitated by two small circular spots 
free from scales and hence clear and transparent. When 
Kallima alights it holds the wings in such position that the 
combination of all four produces with remarkable fidelity 
the simulation of a dead leaf still attached to the twig by 
a short pedicel or leaf-stalk (imitated by a short "tail ' 
on the hind wings). The head and legs of the butterfly 
are concealed beneath the wings. 

Warning colors, terrifying appearances, and mimicry. 
— While many animals are so colored as to harmonize 
with their habitual or usual environment, others on the 
contrary are very brightly colored and marked in such 
bizarre and striking pattern as to be conspicuous. There 
is no attempt at concealment; it is obvious that conspicu- 
ousness is the object sought or at least produced by the 
coloration. Animals like these, we shall find, are in 
almost all cases specially protected by special weapons of 
defence such as stings or poison-fangs, or by the secretion 
of an acrid, ill-tasting fluid in the body. Many cater- 
pillars have been found, by observation in nature and by 
experiment, to be distasteful to insectivorous birds. Now 
it is obvious that it would be advantageous to these cater- 
pillars to be readily recognized by birds. After a few 
trials the bird learns by experience to let these distasteful 
larvae alone ; their conspicuous markings serve as warning 
colors. The black-and-yel low-banded caterpillar of the 
common milkweed or monarch butterfly {A nosia plexip- 
pus) is a good example of such protection by a combina- 



COLOR AND PROTECTIVE RESEMBLANCES 



431 



tion of distastefulness and warning coloration. The little 
lady-bird beetles are mostly distasteful to birds ; they are 
brightly and conspicuously marked. Certain little Nica- 
raguan frogs have a bright livery of red and blue, in strong 




Fig. 164. — The larva of the pen-marked sphinx-moth, Sphinx chersis, 
showing terrifying attitude, (After Comstock.) 

contrast to the dull concealing colors of other frogs in 
their region. By offering these little blue and red frogs 
to hens and ducks the naturalist Belt found that they are 
distasteful to the birds. 

Certain animals which are without special means of 
defence and are not distasteful are yet so marked or 
shaped and so behave as to present a threatening or 
terrifying appearance. The large green caterpillars of 
the sphinx-moths, the tomato- and tobacco-worms, are 



43 2 ELEMENTARY ZOOLOGY 

familiar examples, each larva having a sharp horn on the 
back of the next to last body-segment (fig. 164). When 
disturbed the caterpillar assumes a threatening attitude, 
and the horn seems to be an effective weapon of defence. 
As a matter of fact it is not at all a weapon of defence, 
being weak, not provided with poison, and altogether 
harmless. 

But it would plainly be to the advantage of a defence- 
less animal, one without poison-fangs or sting and without 
an ill-tasting substance in its body, to be so marked and 
shaped as to mimic some other specially defended or 
inedible animal sufficiently to be mistaken for it and thus 
to escape attack. Such cases have been noted, especially 
among insects. This kind of protective resemblance may 
be called mimicry. A most striking case is that presented 
by the familiar monarch and viceroy butterflies (fig. 165). 
The monarch {Anosia plexippus) is perhaps the most 
abundant and widespread butterfly of our country. It is 
a fact well known to entomologists that it is distasteful to 
birds and is let alone by them. It is conspicuous, being 
large and chiefly red-brown in color. The viceroy 
{Basilar chia ar chip pas), also red-brown and patterned 
almost exactly like the monarch, is not, as its appearance 
would seem to indicate, a very near relation of the latter, 
but on the contrary it belongs to a genus of butterflies 
all of which, except the viceroy and one other, are black 
and white in color and of different pattern from the 
monarch. The viceroy is not distasteful to birds, but by 
its extraordinary simulation or mimicking of the monarch 
it is not distinguished from it and so is not molested. In 
the tropics there have been discovered numerous examples 
of mimicry among insects. The members of two large 
families of butterflies (Danaidae and Heliconidae) are dis- 
tasteful to birds and are mimicked by members of other 
butterfly families (especially the Pieridae). 



COLOR AND PROTECTIVE RESEMBLANCES 



4.S 



oo 



Alluring coloration. — A few animals show what is 
called alluring coloration; that is, they display a color 
pattern so arranged as to resemble or mimic a flower or 
other lure, and thus entice to them other animals, their 




Fig. 165. — The monarch butterfly. Anosia plexippns (above), distasteful to 
birds, and the viceroy. Basilarchia archippus (below), which mimics it. 
From specimens.) 

natural prey. Certain Brazilian fly-catching birds have a 
brilliantly colored crest which can be displayed in the 
shape of a flower-cup. The insects attracted by the false 
flower furnish the bird with food. In the tribe of fishes 
called the "anglers" or " fishing frogs, ' ' the front rays 
of the dorsal fin are prolonged in the shape of long slender 
filaments, the foremost and longest of which has a flat- 
tened and divided extremity. The angler conceals itself 
in the mud or in the cavities of a coral reef, and waves 
the filament back and forth. Small fish are attracted 



434 ELEMENTARY ZOOLOGY 

by the lure, mistaking it for worms writhing about. When 
they approach they are engulfed in the mouth of the 
angler, which in some species is of enormous size. One 
of these angler species is known to fishermen as the 
"all-mouth." 

For a fuller account of protective resemblances and 
mimicry see Jordan and Kellogg's "Animal Life," pp. 
201-223. For still more extended accounts see Poulton's 
" Colours of Animals," and Beddard's " Animal Colora- 
tion." 



CHAPTER XXXII 
THE DISTRIBUTION OF ANIMALS 

Technical Note. — The larger aspects or phenomena of the dis- 
tribution of animals over the earth on land and in sea cannot be 
studied personally in the field by the student, but many local fea- 
tures of distribution can be so observed and studied. The restric- 
tion of certain kinds of animals to certain kinds of habitat, the 
presence and character and effectiveness of barriers, some of the 
modes of distribution, the presence and successful life of introduced 
foreign species such as the black and brown rats, the English 
sparrow, the German and Asiatic cockroaches, the gradual change 
of range or distribution of certain kinds of animals through the in- 
fluence of a change in environment (caused by man in cutting off 
forests, cultivating heretofore wild pastures, etc.) all offer favorable 
and profitable opportunities for personal observation. 

An excellent and feasible piece of field-work in distribution is the 
making of a zoological survey of the locality in which the school is 
situated. A map of the locality should be made on a generous 
scale, which should include all prominent physical features of the 
region, such as streams, ponds, hills, woodlands, marshes, etc., 
and on this map should be indicated the places where the various 
animals of the local fauna occur. Some of the animal species will 
have a limited range, and the limits of this range should be shown. 
This map and faunal list can be added to and perfected by succes- 
sive classes. For fuller discussions of the geographical distribution 
of animals see Jordan and Kellogg's " Animal Life," Beddard's " Zoo- 
geography," Heilprin's " The Distribution of Animals," and Wallace's 
"Geographical Distribution." 

Geographical distribution. — It is a matter of common 
knowledge with ail of us that there are no wild lions or 
camels or kangaroos or monkeys or ostriches or night- 
ingales in North America. Ostriches are found only in 
Africa and South America, kangaroos only in Australia, 

435 



43 6 ELEMENTARY ZOOLOGY 

lions only in Asia and Africa. On the other hand there 
are no opossums in Europe or grizzly bears or rattlesnakes 
anywhere else in the world than in this country. That 
is, certain kinds of animals have a certain limited range of 
occurrence or distribution. It is obvious, too, that certain 
animals live only on land, while others live only in water, 
and of these latter some are restricted to the ocean, while 
others live only in fresh water. All of the facts regard- 
ing the dispersion or diffusion of animals on land and in 
water make up the science of the geographical distribution 
of animals, or, as it is sometimes called, zoogeography. 
Under this subject are included not only the facts of the 
present actual distribution or occurrence of animals over 
the world, but the facts concerning the reasons for this 
distribution, the modes of travel and dispersion, the char- 
acter and influence of barriers to the spread, and the 
results, in the adaptation of old forms and the production 
of new forms, of the phenomena of distribution. 

Just as maps are made to show graphically the facts of 
political geography, w T hich concerns the position and 
extent of the various powers and States which claim 
the allegiance of the people, and the facts of physical 
geography, which concerns the physical character of the 
earth's surface, so maps are made to show the geograph- 
ical distribution of animals. Because of the great numbers 
of animal species no one map can show the distribution 
of all species, but a series of maps of the world or of a 
continent or of a State or county or more limited region 
could be made (and many such have been made) showing 
the distribution of selected species. In a map of a limited 
locality, say of a few square miles, the occurrence and 
distribution of most of the commoner and more familiar 
animals can be shown, and each high school should 
possess such a map (see technical note at beginning of 
this chapter). 



THE DISTRIBUTION OF ANIMALS 437 

Laws of distribution. — The laws governing the distri- 
bution of animals over the earth's surface have been 
recently * expressed in a simple statement as follows : 
Every species of animal is found in every part of the earth 
unless (a) its individuals have been unable to reach this 
region on account of barriers of some sort; or (J?) having 
reached it, the species is unable to maintain itself, through 
lack of capacity for adaptation, through severity of com- 
petition with other forms, or through destructive conditions 
of environment; or (c) having entered and maintained 
itself it has become so altered in the process of adaptation 
as to become a species distinct from the original type. 

Modes of migration and distribution. — That animals 
should be continually trying to extend their range is 
obvious from what we know of their rapid increase by 
multiplication. In a region which can provide food for 
but one thousand wolves, there is a production each year 
of several times one thousand. These new wolves must 
struggle among themselves for food, or migrate, if possi- 
ble, to new regions as yet not inhabited by wolves. The 
wolfs mode of migration or distribution is walking or 
running, and so with other mammals except the bats and 
aquatic forms. Birds and bats can fly, and can thus 
migrate more swiftly, farther, and over barriers which 
would stop mammals. Most insects can fly. Worms 
can only crawl and very slowly at that. Fishes can swim, 
but if they are in a landlocked sheet of water, they cannot 
go beyond its confines. Marine animals can migrate 
from ocean to ocean, and land animals from continent to 
continent unless checked by barriers (see next para- 
graph). 

But besides such voluntary and independent modes of 
distribution long journeyings may be made involuntarily, 
or by a passive migration as it may be called. Parasites, 

* Jordan and Kellogg's ;i Animal Life," 1900, p. 274. 



43 8 ELEMENTARY ZOOLOGY 

for example, are carried by their hosts in all their travels; 
the tiny Tardigrada and Rotifera, which can be desiccated 
and yet restored to active life by coming again into water, 
are carried in the dried mud on the feet of birds or other 
animals. On floating objects in rivers or in ocean cur- 
rents land-animals may be carried long distances. Man, 
the greatest traveller of all, is responsible for the widened 
distribution of many animals. Thus have come to us in 
ships from Europe the black and brown rats, the English 
sparrow, the Hessian fly, the commonest cockroaches of 
our houses and many other forms. And these animals 
have been carried involuntarily all over the United States 
in railway-cars and wagons. 

Barriers to distribution. — As is indicated in the para- 
graph on the modes of migration, a considerable sheet of 
water is obviously a barrier to the further travelling of a 
walking or crawling land-animal, although no barrier to 
a winged form. Similarly a strip of land is a barrier to a 
strictly aquatic animal as a fish. Or a high fall in the 
stream may serve as an insuperable barrier, making it im- 
possible for any fish below the fall to reach the upper 
part of the stream. Numerous cases of this kind are 
known in the Rocky Mountains and Sierra Nevada, where 
a stream may be well supplied with trout below a fall, 
and quite bare of these fish above the fall. In the 
Yosemite Valley in California trout live in the Merced 
River below the great Vernal and Nevada falls, but above 
these falls the Merced contains no trout. To fresh-water 
swimming animals salt water may be a barrier; thus some 
kinds of fresh-water fishes are limited to one of two 
near-by streams although the mouths of these streams 
empty near each other into the ocean. The amphibious 
batrachians, at home in fresh water and on land, are 
killed by contact with sea-water. Earthworms also are 
killed by salt water. Thus the narrowest ocean strait is 



THE DISTRIBUTION OF ANIMALS 439 

as effective a barrier to these animals as a whole sea. 
High mountain ranges and broad deserts are barriers to 
many land-animals, partly because of the physical ob- 
stacles, partly because of the differences in temperature 
and in food-supply. 

Temperature and climate (as distinct from temperature) 
and the ocean are the three great barriers when we con- 
sider the animal kingdom as a whole, and look for the 
causes which determine the chief zoogeographical divisions 
of the earth's surface. Most of the tropical animals 
cannot endure frost, hence the isothermal line of frost is 
a line across which few tropical animals venture. Most 
arctic animals are enfeebled by heat, and the isothermal 
line which marks off the region in which frost occurs the 
year round is another great zoogeographical boundary. 
But while these lines are limits for localized species, some 
animals, as birds, especially, keep within a relatively 
uniform temperature by migrations across these lines. It 
should be borne in mind that the gradual decrease in 
temperature met with in going north or south from the 
tropics is also met in the ascent of high mountains. The 
summits of lofty peaks, even in the tropics, are truly 
arctic in character; they are snow-covered, and the 
animals and plants on them are truly arctic. Thus in the 
ascent of a single mountain a whole series of life-zones 
from tropical to arctic can be traversed. 

Climate, as distinct from temperature, establishes limits 
of distribution. The animals of Eastern North America 
accustomed to a humid atmosphere cannot live in the dry 
plains and deserts of the West. Closely associated with 
climate is the nature of the plant-growth covering the 
land; here are forests and luxuriant meadows, there are 
sparse tough grasses of the dry plateau. The limits of a 
special kind of plant-growth often are the limits of distri- 
bution of certain animals. 



44o ELEMENTARY ZOOLOGY 

The third great barrier, the ocean, is perhaps the most 
obvious of all in its influence. It is only in rare cases 
that any land-animal can independently cross a great 
ocean. Thus the land-animals of Australia differ from 
those of all other countries, and those of Africa and South 
America have developed almost independently of one 
another. The ocean is, as already mentioned, also a 
barrier for fresh-water aquatic animals, and even marine 
fishes which live normally in shallow waters along the 
shore rarely venture across the great depths of mid-ocean. 

The obstacles or barriers met with determine the limits 
of a species. Each species broadens its range as far as it 
can. It attempts unwittingly, through natural processes 
of increase, to overcome the obstacles of ocean or river, 
of mountain or plain, of woodland or prairie or desert, of 
cold or heat, of lack of food or abundance of enemies — 
whatever the barriers may be. The degree of hindrance 
offered by any barrier differs with the nature of the animal 
trying to pass it. That which forms an impassable 
obstacle to one species may be a great aid to the spread 
of another. " The river which blocks the monkey or the 
cat is the highway of the fish and turtle. The waterfall 
which limits the ascent of the trout is the chosen home of 
the ouzel. " 

Faunae and zoogeographic areas. — The term fauna is 
applied to the animals of any region considered collect- 
ively. Thus the fauna of Illinois includes the entire list 
of animals found naturally in that State. The fauna of a 
schoolyard comprises all the animals found living naturally 
in the yard. The fauna of a pond includes all the animal 
inhabitants of the pond. {Flora is used similarly of all 
the plants in a given region.) The relation of one fauna 
to another depends on the character and effectiveness of 
the barriers between, and the physical character of the 
two regions. Thus the fauna of Illinois differs but little 



THE DISTRIBUTION OF ANIMALS 441 

from that of Indiana or Iowa, because there are no barriers 
between the States, and they are alike physically. On 
the other hand the fauna of California differs much from 
that of the Eastern States because of the great barriers 
(the desert and the Sierra Nevada Mountains) which lie 
between it and these States, and because of the great 
differences in the physical and climatic conditions of the 
two regions. 

The land-surface of the earth has been divided by 
zoogeographers into seven great realms of animal life, 
based on the distributional characters shown by these 
various regions. These realms are separated by barriers 
of which the chief are the presence of the sea and the 
occurrence of frost. These realms are named, from their 
geographical region, the Arctic, the North Temperate, 
the South American, the Indo-African, the Madagascar, 
the Patagonian, and the Australian. Of these the 
Australian alone is sharply defined. Most of the others 
are surrounded by a broad fringe of debatable ground 
that forms a transition to some other zone. 

Habitat and species. — The habitat of a species of 
animal is the region in which it is found in a state of 
nature. It is currently believed that the habitat of any 
animal is the whole of that region for which it is best 
adapted. But this is not necessarily true. In fact in 
most cases it is not true. The trout naturally debarred 
from the rivers in Yellowstone Park by the waterfalls 
could live there well if the barrier could be passed. In 
the case of one stream it has been passed and the trout 
flourish above the fall. The success of the black and 
brown rats and the English sparrow in America, of the 
rabbit in Australia, of bumblebees and house-flies in New 
Zealand, all of which animals had a natural habitat not 
including these regions, but by artificial means have been 
carried over the barriers and into che new territory, prove 



442 ELEMENTARY ZOOLOGY 

that ' ' habitat ' ' is not necessarily coincident with ' ' only 
fit region.' Shad, striped bass, and catfish from the 
Potomac River have been introduced into and now thrive 
in the Sacramento River in California. In fact the whole 
work of the introduction and diffusion of valuable food- 
animals in territory not naturally included in the habitat 
of the species is based on our knowledge that the habitat 
of a species is often determined by physical barriers rather 
than by exclusive fitness of environment. Within the 
natural habitat the environment is fit for the species' 
existence, outside of it the environment may be fit. 

But there occur numerous instances where a species 
successful in leaving its orignal habitat is unsuccessful in 
attempting to maintain itself on new ground. Man has 
introduced various animals from one country to another. 
The English sparrow (naturally debarred from this country 
by the ocean barrier), brought to America from Europe, 
has covered its new territory rapidly and maintains itself 
with brilliant success. But the nightingale, the starling 
and skylark which have been repeatedly introduced and 
set free are unable to maintain themselves here. 

Species-extinguishing and species-forming.— Accom- 
panying the constant slow migrating of species into new 
habitats and the constant slow changing of environment 
and conditions everywhere is to be seen a constant modi- 
fication of the fauna of any region due to the inability of 
some species to maintain their ground, the predominating 
increase of others, and the modifying or adaptive chang- 
ing of others into new forms. In 1544 the black rat of 
Europe was introduced into America and it soon crowded 
out the native rats, being in its turn crowded out by the 
European brown rat (the present common rat in buildings), 
introduced about 1775. Here we have the original native 
species unable to maintain itself in competition with in- 
troduced forms. 



THE DISTRIBUTION OF ANIMALS 443 

With a change of environing conditions, certain species 
are unable to maintain themselves. With the destruction 
of the forests going on in parts of our country the great 
host of wood-creatures, the bears, squirrels, the wood- 
birds and insects, can no longer maintain themselves, and 
grow rare and disappear. Man often also influences the 
status of a species by checking its increase either by 
actual slaughter, as with the bison and passenger-pigeon, 
or by making adverse changes in its environment, as by 
destroying forests, or putting the plains under cultivation. 

In the discussion of " species-forming " (see p. 408) it 
was shown that adaptation may lead to the altering of 
species, and to the formation of new ones (under the in- 
fluence of natural selection). With the gradual change of 
conditions, or with the facing of new conditions because 
of an unusual migration to or invasion of new territory, 
those individuals of the species exposed to the new con- 
ditions must adapt themselves in structure and habit in 
order to meet successfully the new demands. By the 
cumulative action of natural selection these adaptive 
changes are emphasized ; and this emphasis may come to 
be so pronounced that the part of the species represented 
in this newly acquired territory, if isolated from the orig- 
inal stock, is so altered as to be quite distinct in appear- 
ance from the old. If these changed individuals are also 
physiologically distinct from the old stock, i.e. are 
unable to mate with them, a new species is established. 
As already mentioned, the peopling of islands from main- 
lands is an excellent and readily observable example of 
the phenomena referred to in the third law of distribution. 



APPENDICES 

EQUIPMENT AND METHODS 



APPENDIX I 

EQUIPMENT AND NOTES OF PUPILS 

Equipment of pupils. — Each pupil should have a 
laboratory note-book of about 8 X 10 inches, opening at 
the end, in which both drawings and notes can be made. 
The paper should be unruled and of good quality (not too 
soft). Each pupil should have also instruments of his 
own as follows: scalpel, pair of small scissors, spring 
forceps, pair of dissecting-needles, small glass pipette, and 
paper of ribbon-pins for pinning out specimens. The cost 
of this outfit need not exceed $1.00. The laboratory 
should furnish him with a dissecting-dish and a dissecting- 
microscope, or at least a lens. 

Laboratory drawings and notes. — Each pupil should 
make the drawings called for in the directions for the 
laboratory exercises. These drawings should be in out- 
line, and put in by pencil; the lines may be inked over if 
preferred. Shading should be used sparingly, if at all. 
Each drawing and all the organs and animal parts repre- 
sented in it should be fully named. See the anatomical 
plates in this book for example. With such complete 
44 labelling/' little note-taking need be done in connec- 
tion with the dissections. 

Notes should be made of any observations which cannot 
be represented in the drawings; for example, on the 

447 



448 APPENDIX 

behavior of the living animals. All notes referring to 
matters of life-history should be dated. 

Field-observations and notes. — Scattered through this 
book will be found numerous suggestions for student field- 
work, for the observation of the life-history and habits and 
conditions of animals in nature. As explained in the 
Preface, the initiation and direction of such work must 
be left to the teacher. But its importance both because 
of its instructiveness and its interest is great. Pupils 
should not only be incited to make individual observations 
whenever and wherever they can, but the teacher should 
make little field-excursions with the class or with parts of 
it at various times, to ponds or streams or woods, and 
1 ' show things' to all. The life-history and feeding- 
habits of insects, the web-making of spiders, the flight, 
songs, nesting, and care of young of birds, the haunts of 
fishes, the development of frogs, toads, and salamanders, 
the home-building and feeding-habits of squirrels, mice, 
and other familiar mammals are all (as has been called 
attention to at proper places in the book) specially fit 
subjects for field-observation. 

Each pupil should keep a field note-book, recording 
from day to day, under exact date, any observations he 
may make. Let the most trivial things be noted; when 
referred to later in connection with other notes they may 
not seem so trivial. The field note-book should be 
smaller than the laboratory note- and drawing-book, 
small enough to be carried in the pocket. Notes should 
be made on the spot of observation ; do not wait to get 
home. Sketches, even rough ones, may be advanta- 
geously put into the book. Students with photographic 
cameras can do some very interesting and valuable field- 
work in making photographs of animals, their nests and 
favorite haunts. Such photographic work is very effectively 
used now in the illustration of books about animals and 



EQUIPMENT AND NOTES OF PUPILS 449 

plants (see the reproductions of photographs in this book). 
If the class is making a collection the collecting notes or 
data made in the field-books of the different pupil collec- 
tors should all be transferred to a common " Notes on 
Collections " book kept by the whole class. 



APPENDIX II 

LABORATORY EQUIPMENT AND METHODS 

Equipment of laboratory. — The equipment of the 
laboratory or classroom will, of necessity, depend upon the 
opportunities afforded the teacher by the school officers to 
provide such facilities as instruments, books, and charts. 
If dissections are to be seriously and properly made, 
however, some equipment is indispensable. Flat-topped 
tables, not over 30 inches high, a few compound micro- 
scopes (one is much better than none), as many simple 
lenses, or, far better, simple dissecting-microscopes, as 
there are students, dissecting-dishes, a pair of bone- 
clippers, one injecting-syringe, a bunch of bristles, water, 
a few simple reagents and some inexpensive glassware, 
as slides, cover-glasses, watch-crystals, and fruit- or 
battery-jars for live cages and aquaria, make up a suffi- 
cient equipment for good work. Much can be done with 
less, and perhaps a little more with some additional 
facilities. 

The dissecting-pans should be of galvanized iron or tin, 
oblong, about 6x8 inches by 2 inches deep, with 
slightly flaring sides. If an iron wire be run around the 
margin, and the margin bent back over it, it will 
strengthen the dish, and make a broader and smoother 
edge for the hands to rest on. Diagonally across the 
dish, about one-fourth inch from the bottom, should run a 
thick wire. A layer of paraffin one-half inch thick 

45o 



LABORATORY EQUIPMENT AND METHODS 45 1 

should cover the bottom. It should be poured in melted, 
when the diagonal wire will be imbedded in it and will 
hold it in place. Acids must not be put into the pan. 

The reagents necessary are alcohol of 95 per cent and 
85 per cent, and formalin of 4 per cent (the formaldehyde 
sold by druggists is 40 per cent and should be diluted ten 
times with water), these for preserving material for dis- 
section; chloroform for killing specimens; glycerin for 
making temporary microscopic mounts, and 20 per cent 
nitric acid for preparing specimens for study of the nervous 
system* In addition there will be needed the few other 
materials mentioned in the following paragraphs as neces- 
sary in the preparation of injecting-fluids, the staining of 
fresh tissue and preserving by special methods. 

A list of reference books desirable in the laboratory is 
appended as a separate paragraph (see p. 454). 

Collecting and preparing material for use in the 
laboratory. — As directions have been given in the " tech- 
nical notes " scattered through the book for the collecting 
and preparing of all the various kinds of animals chosen 
as subjects of the laboratory exercises, it will only be 
necessary to give here directions for making certain 
special mixtures and for the special preparation of speci- 
mens by injection, etc. Specimens to be used for dissec- 
tion should be kept in alcohol of 85 per cent or in formalin 
of 4 per cent. Alcohol is better for the earthworm, but 
for the other examples formalin is either better or as good, 
and as it is much cheaper it may well be chosen for the 
general preservative. 

Methyl gi'een, a stain used for coloring fresh tissues. 
Dissolve the methyl green powder in water, using about 
as much powder as the water will take up. Add a few 
drops of acetic acid. 

Iiijccting-masses. — Injections are best made with prep- 
arations of French gelatine, but white glue will answer 



45 2 APPENDIX II 

most purposes. For fine injection use a combination of 
the following: I part of a solution of gelatine, I part to 
4 parts of water ; i part of a saturated solution of lead 
acetate in water, and I part of a saturated solution of 
potassium bichromate in water. A mixture of these when 
hot gives a beautiful yellow injection-mass which, filtered, 
will pass through the finest capillaries. For different 
colorings use dry paints, which come in ultramarine blue, 
vermilion, and green. The gelatine should be thoroughly 
soaked before the coloring-matter is added. A mistake 
is generally made in using the injection-mass too thick. 
One part by weight of gelatine to six or even more parts 
of water is a good proportion. The gelatine as well as 
glue-masses should be made in a water-bath, which con- 
sists of one dish placed within another outer one contain- 
ing warm water. The mass should be injected warm, not 
hot, after which the injected specimen is to be placed in 
cold water until the injecting-mass has set. Glue (the 
ordinary white kind) can be used for most injections just 
as the gelatine was used, but should not be so much 
diluted. All injection-masses should be filtered through 
a cloth before using. 

Preparing skeletons — In general, skeletons are best 
cleaned by boiling. After most of the flesh has been cut 
away the skeleton should be boiled in a s*oap solution 
until the remaining parts of the muscles are thoroughly 
softened. The soap solution is made of 2,000 c.c. of 
water, preferably distilled, 12 grams of s ltpetre, and 75 
grams of hard soap (white). Heat the until dissolved, 
then add 150 c.c. of strong ammonia. This stock solu- 
tion is mixed with four or five parts of water, when the 
mixture is ready for use. The bones after boiling are 
rinsed in cold water, brushed and picked clean, then left 
to dry on a clean surface. 

Preserving anatomical preparations — Many specimens 



LABORATORY EQUIPMENT AND METHODS 453 

worth keeping will be found, and for them a solution 
known as Fischer's formula is suggested as good, especially 
for brains. Fischer's formula is made up as follows: 
2,000 c.c. of water, 50 c.c. of formalin, 100 grams of 
sodium chloride, and 15 grams of zinc chloride. These 
are mixed together until thoroughly dissolved. Open 
preparations well before placing them in the liquid and 
use about twenty times the volume of the object to be 
preserved. 

To keep fresh dissections. — For materials which are 
dissected fresh and must be kept over for several days in 
a fresh condition add a few drops of carbolic acid to the 
water which covers them. Carbolized water (2 per cent 
in water) will preserve a great many tissues for a long 
time. Hearts will remain for years in a supple condition 
in this solution. 

Obtaining marine animals, microscopic preparations, 
etc. — For schools not on the seashore the marine animals 
such as starfishes, etc., which are to be dissected or 
examined as examples of the branches to which they 
belong must be obtained as preserved specimens from 
dealers in such supplies. Among such dealers on the 
Atlantic coast are the Marine Biological Laboratory, 
Woods Holl, Mass. ; F. W. Walmsley, Academy of 
Natural Sciences, Philadelphia, Pa. ; and H. H. and C. S. 
Brimley, Raleigh, N. C. ; on the Pacific coast the Supply 
Department, Hopkins Seaside Laboratory, Stanford Uni- 
versity, California. Ward's Natural Science Establish- 
ment, Rochester, N. Y., supplies almost any biological 
specimens asked for. This establishment furnishes already 
made dissections and sets illustrating life-history and 
metamorphosis. The few permanent microscopic prepara- 
tions which are mentioned in the book as desirable to have 
can be made by the teacher if he has had any training in 
microscopical technic. If not, they may be bought 



454 APPENDIX II 

cheaply of such dealers in natural history supplies as the 
Bausch & Lomb Optical Co., Rochester, N. Y. ; the 
Kny-Scheerer Co., 17 Park Place, New York City; 
Queen & Co., 1010 Chestnut Street, Philadelphia, Pa., 
and numerous others. From these dealers also can be 
bought all of the laboratory supplies, such as lenses, 
slides, cover-glasses, dissecting-scalpels, scissors and 
needles, etc., mentioned in this book. 

Reference books. — Throughout the preceding chapters 
exact references have been made to various books, as 
many of which as possible should be in the school-library- 
Some of these references have been made with special 
regard to the teacher, but most with special regard to the 
pupil. All of the books referred to are included in the 
following list. For the convenience of the prospective 
buyer, the names of the publishers and prices of the books 
are appended. In buying books, it is of course not 
necessary to order from the various publishers. A list of 
the books desired may be handed to any book-dealer, who 
will order them and who should in most cases be able to 
get them for a little less than publisher's list prices. 

Baskett, J. N. The Story of the Birds. 1899, D. Appleton & Co. $0.65. 
Beddard, Frank. Animal Coloration. 1892, Macmillan Co. $3.50. 

Zoogeography. 1895, Macmillan Co, $1.60. 

Bendire, Chas. Directions for Collecting, Preparing, and Preserving Birds' 

Eggs and Nests. Distributed by U. S. National Museum. 
Bird Lore, an Illustrated Journal about Birds. Macmillan Co. $1.00 a 

year. 
Cambridge Natural History, Vols. V (Peripatus), $4.00, VI (Insects), 

$3.50. Macmillan Co. 
Chapman, Frank. Handbook of the Birds of Eastern North America. 

1899. D. Appleton & Co. $3.00. 
ComstOCk, J. H. Manual for the Study of Insects. 1897, Comstock Pub. 

lishing Co. $3.75. 

Insect Life. 1901, D. Appleton & Co. $1.50. 

and Kellogg, V. L. Elements of Insect Anatomy. 1901, Comstock 

Publishing Co. $1.00. 



LABORATORY EQUIPMENT AND METHODS 45i 

Cooke, W. W. Bird Migration in the Mississippi Valley. Distributed by 

the Division of Biological Survey, U. S. Dept. Agric. 
Cowan, T. W. Natural History of the Honey-bee. 1890, London: Houls- 

ton. is. 6d. 
Coues, Elliott. Key to North American Birds. 1890, Estes and Lauriat. 

$7.50. 
Darwin, Chas. The Formation of Vegetable Mold through the action of 

Worms. D. Appleton & Co. $1.50. 

Origin of Species. 1896, Caldwell. $0.75. 

The Structure and Distribution of Coral Reefs. D. Appleton & Co. 

$2.00. 

Plants and Animals under Domestication. D. Appleton & Co. 

Davie, Oliver. Methods in the Art of Taxidermy. 1894, Oliver Davie & 

Co., Columbus, O. $10 net. 
Gage, S. H. Life History of the Toad. Teacher's Leaflets No. 9, April, 

1898, prepared by College of Agriculture, Cornell University, Ithaca, 

N. Y. 
Heilprin, A. The Distribution of Animals. 1886, D. Appleton & Co. 

$2.00. 
Hodge, C. F. The Common Toad. Nature Study Leaflet, Biology Series 

No. 1, 1898, published by C. H. Hodge, Worcester, Mass. 
Holland, W. J. The Butterfly Book. 1899, Doubleday and McClure Co. 

$3.00. 
Hornaday, W. T. Taxidermy and Zoological Collecting. 1897, Chas. 

Scribner's Sons. $2.50 net. 
Howell, W. H. Dissection of the Dog. 1889, Henry Holt & Co. $1.00. 
Huxley, T. H. The Crayfish : an introduction to the Study of Zoology. 

D. Appleton & Co. $1.75. 
Jordan, D. S. Manual of Vertebrate Animals of the Northern United 

States, 8th ed. 1899, A. C. McClurg & Co. $2.50. 
and Evermann, B. W. Fishes of North and Middle America, 4 vols. 

1898-1900, Distributed by U. S. National Museum. 

and Kellogg, V. L. Animal Life. 1900, D. Appleton & Co. $1.20. 

Lubbock, John. Ants, Bees, and Wasps. 1882. D. Appleton & Co. $2.00. 
Marshall, H. M., and Hurst, C. H. Practical Biology, 5th ed. G. P. Put- 
nam's Sons. $3.50. 
Martin, H. W., and Moale, W. A. Handbook of Vertebrate Dissection, 3 

parts. 1881, Macmillan Co. 

Part I. How to dissect a Chelonian (red-bellied slider terrapin); 
Part 2. How to dissect a bird (pigeon); 
Part 3. How to dissect a rodent (rat). 
McCook, Henry. American Spiders and their Spinning Work, 3 vols. 

1889-1893, H. C. McCook. Phila., Pa. $30.00. 
Miall, L. C. The Natural History of Aquatic Insects. 1895, Macmillan 

Co. $1.75. 



45 6 APPENDIX II 

Parker, T. J. A Course of Instruction in Zootomy. 1884, Macmillan Co. 

$2.25. 

Lessons in Elementary Biology. 1897, Macmillan Co. $2.65. 

and Haswell, W. A. Textbook of Zoology, 2 vols. 1897, Macmillan 

Co. $9.00. 
Peckham, George W. and E. J. On the Instincts and Habits of the Solitary 

Wasps. 1898, sold by Des Forges & Co., Milwaukee, Wis. $2.00. 
Potts, E. Fresh-water Sponges. 1887, Phil. Acad, of Sciences. 
POulton, E. B. The Colors of Animals. 1890, D. Appleton & Co. $1.75. 
Reighard, J. E., and Jennings, H. S. The Anatomy of the Cat. 1901, 

Henry Holt & Co. $4.00. 
Ridgway, R. Directions for Collecting Birds. Distributed by U. S. 

National Museum. 
Riverside Natural History, 6 vols. Houghton, Mifflin & Co. $30.00. 
Romanes, Geo. Darwin and After Darwin, I. 1895-97, Open Court Pub- 
lishing Co. 
Scudder, S. H. The Life of a Butterfly. 1893, Henry Holt & Co. $1.00. 
Van Beneden, E. Animal Parasites and Messmates. 1876, D. Appleton 

& Co. $1.50. 
Wallace, A. R. The Geographical Distribution of Animals. 1876, Harper 

& Bros. $10.00. 
Wallace, A. R. Island Life. 188 1, Harper & Bros. $4.00. 



APPENDIX III 

REARING ANIMALS AND MAKING COLLEC- 
TIONS 

Much good work in observing the behavior and life- 
history of some kinds of animals can be done by keeping 
them alive in the schoolroom under conditions simulating 
those to which they are exposed in nature. The growth 
and development of frogs and toads from egg to adult, as 
well as their feeding habits and general behavior, can all 
be observed in the schoolroom as explained in Chapter 
XII. Harmless snakes are easily kept in glass-covered 
boxes ; snails and slugs are contented dwellers indoors ; 
certain fish live well in small aquaria, and many other 
familiar forms can be kept alive under observation for a 
longer or shorter time. But from the ease with which 
they are obtained and cared for, the inexpensiveness of 
their live-cages, and the interesting character of their life- 
history and general habits, insects are, of all animals, the 
ones which specially commend themselves for the school- 
room menagerie. In the technical notes in the chapter 
(XXI) devoted to insects are numerous suggestions re- 
garding the obtaining and care of certain kinds of insects 
which may be reared and studied to advantage in the 
schoolroom. In the following paragraphs are given direc- 
tions for making the necessary live-cages and aquaria for 
these insects. 

Live-cages and aquaria. — Prof. J. H. Comstock has 
so well described the making of simple and inexpensive 

457 



458 



APPENDIX III 




Fig. 166. — Soap-box breeding-cage for 
insects. (From Jenkins and Kellogg.) 



cages and aquaria in his book, " Insect Life," that, with 
his permission, his account is quoted here. 

Live-cages. — "A good home-made cage can be built 
by fitting a pane of glass into one side of an empty soap- 
box. A board, three or 
four inches wide, should 
be fastened below the 
glass so as to admit of a 
layer of soil being placed 
in the lower part of the 
cage, and the glass can 
be made to slide, so as to 
serve as a door (fig. 166). 
The glass should fit close- 
ly when shut, to prevent 
the escape of the insects. 
"In rearing caterpillars and other leaf-eating larvae, 
branches of the food-plant should be stuck into bottles or 
cans which are filled with sand saturated with water. By 
keeping the sand wet the plants can be kept fresh longer 
than in water alone, and the danger of the larvae being 
drowned is avoided by the use of sand. 

"Many larvae when full-grown enter the ground to 
pass the pupal state ; on this account a layer of loose soil 
should be kept in the bottom of a breeding-cage. This 
soil should not be allowed to become dry, neither should 
it be soaked with water. If the soil is too dry the pupae 
will not mature, or if they do so the wings will not expand 
fully; if the soil is too damp the pupae are liable to be 
drowned or to be killed by mold. 

" It is often necessary to keep pupae over winter, for a 
large proportion of insects pass the winter in the pupal 
state. Hibernating pupae may be left in the breeding- 
cages or removed and packed in moss in small boxes. 
Great care should be taken to keep moist the soil in the 



REARING ANIMALS AND MAKING COLLECTIONS 459 



^S 



breeding-cages, or the moss if that be used. The cages 
or boxes containing the pupae should be stored in a cool 
cellar, or in an unheated room, or in a large box placed 
out of doors where the sun cannot strike it. Low tem- 
perature is not so much to be 
feared as great and frequent 
changes of temperature. 

1 ' Hibernating pupae can be 
kept in a warm room if care be 
taken to keep them moist, but 
under such treatment the mature 
insects are apt to emerge in 
midwinter. 

' ' An excellent breeding-cage 
is represented by fig. 167. It 
is made by combining a flower- 
pot and a lantern-globe. When 
practicable, the food-plant of 
the insects to be bred is planted 
in the flower-pot ; in other cases 
a bottle or tin can filled with 
wet sand is sunk into the soil 
in the flower-pot, and the stems of the plant are stuck into 
this wet sand. The top of the lantern-globe is covered 
with Swiss muslin. These breeding-cages are inexpen- 
sive, and especially so when the pots and globes are 
bought in considerable quantities. A modification of this 
style of breeding-cage that is used by the writer differs 
only in that large glass cylinders take the place of the 
lantern-globes. These cylinders were made especially 
for us by a manufacturer of glass, and cost from six to 
eight dollars per dozen, according to size, when made in 
lots of fifty. 

' ' When the transformation of small insects or of a small 
number of larger ones are to be studied, a convenient 




Fig. 167. — Lamp-chimney and 
flower-pot breeding-cage for 
insects. (From Jenkins and 
Kellogg.) 



460 APPENDIX III 

cage can be made by combining a large lamp-chimney 
with a small flower-pot. 

" The root-cage. — For the study of insects that infest 
the roots of plants, the writer has devised a special form 
of breeding-cage known as the root-cage. In its simplest 
form this cage consists of a frame holding two plates of 
glass in a vertical position and only a short distance apart- 
The space between the plates of glass is filled with soil in 
which seeds are planted or small plants set. The width 
of the space between the plates of glass depends on the 
width of two strips of wood placed between them, one at 
each end, and should be only wide enough to allow the 
insects under observation to move freely through the soil. 
If it is too wide the insects will be able to conceal them- 
selves. Immediately outside of each glass there is a piece 
of blackened zinc which slips into grooves in the ends of 
the cage, and which can be easily removed when it is 
desired to observe the insects in the soil. 

"Aquaria. — For the breeding of aquatic insects aquaria 
are needed. As the ordinary rectangular aquaria are 
expensive and are liable to leak we use glass vessels 
instead. 

" Small aquaria can be made of jelly-tumblers, glass 
finger-bowls, and glass fruit-cans, and larger aquaria can 
be obtained of dealers. A good substitute for these is 
what is known as a battery-jar (fig. 168). There are 
several sizes of these, which can be obtained of most 
dealers in scientific apparatus. 

"To prepare an aquarium, place in the jar a layer of 
sand; plant some water-plants in this sand, cover the sand 
with a layer of gravel or small stones, and then add the 
required amount of water carefully, so as not to disturb 
the plants or to roil the water unduly. The growing 
plants will keep the water in good condition for aquatic 
animal life, and render changing of the water unnecessary, 



REARING ANIMALS AND MAKING COLLECTIONS 461 



if the animals in it live naturally in quiet water. Among 
the more available plants for use in aquaria are the fol- 
lowing: 

" Waterweed, Elodca canadensis. 

' * Bladder wort, Utricularia (several species). 

44 Water -starwort, Callitriclic (several species). 

"Watercress, Nasturtium officinale, 

4t Stoneworts, Char a and Nitella (several species of 
each). 

44 Frog-spittle or water-silk, Spirogyra. 

li A small quantity of duckweed, Lemna, placed on the 
surface of the water adds to the beauty of an aquarium. 




I ftp 




Fig. 168. — Battery-jar aquarium. (From Jenkins and Kellogg.) 

" When it is necessary to add water to an aquarium on 
account of loss by evaporation, rain water should be used 
to prevent an undue accumulation of the mineral-water 
held in solution in other water." 

Making collections. — Much is to be learned about 
animals by "collecting' them. But the collecting 



462 APPENDIX III 

should be done chiefly with the idea of learning about the 
animals rather than with the notion of getting as many 
specimens as possible. To collect, it is necessary to find 
the animals alive; one learns thus their haunts, their local 
distribution, and something of their habits, while by con- 
tinued work one comes to know how many and what 
different kinds or species of each group being collected 
occur in the region collected over. Collecting requires 
the sacrifice of life, however, and this will always be kept 
well in mind by the humane teacher and pupil. Where 
one set of specimens will do, no more should be collected. 
The author believes that high-school work in this line 
should be almost exclusively limited to the building up 
of a common school collection. Let a single set of speci- 
mens be brought together by the combined efforts of all 
the members of the class, and let it be well housed and 
cared for permanently. Each succeeding class will add 
to it ; it may come in time to be a really representative 
exhibition of the local fauna. 

The high-school collection should include not only 
adult specimens of the various kinds of animals, forming 
a systematic collection, as it is called, but also all kinds 
of specimens which illustrate the structure and habits of 
the animals in question and which will constitute a 
so-called biological collection. Specimens of the eggs 
and all immature stages; dissections preserved in alcohol 
or formalin showing the external and internal anatomy; 
nests, cocoons, and all specimens showing the work and 
industries of the various animals ; in short, any specimen 
of the animal itself in embryonic or postembryonic con- 
dition, or any parts of the animal, or anything illustrating 
what the animal does or how it lives, all these should be 
collected as assiduously as the adult individuals. Each 
specimen in the collection should be labelled with the 
name of the animal, the date, and locality, and the name 



REARING ANIMALS AND MAKING COLLECTIONS 463 



of the collector, with any particular information which 
will make it more instructive. If such special data are 
too voluminous for a label, they should be written in a 
general note-book called " Notes on Collections" (kept 
in the schoolroom with the collection), the specimen and 
corresponding data being given a common number so that 
their association may be recognized. In the following 
paragraphs are given brief directions for catching, pinning 
up, and caring for insects, 
for making skins of birds 
and mammals, and for 
the alcoholic preservation 
of other kinds of animals. 
Bisects. — For catching 
insects there are needed 
a net, a killing-bottle, a 
few small vials of alcohol, 
and a few small boxes to 
carry home live speci- 
mens, cocoons, galls, etc. 
For preparing and pre- 
serving the insects there 
are needed insect-pins, 
cork- orpith-lineddrawers 
or boxes, and small wide- 
mouthed bottles of alco- 
hol. 




Fig. 169. — Insect killing-bottle; cyanide 



of potassium at bottom, covered with 
plaster of Paris. (From Jenkins and 
Kellogg.) 



The net, about 2 feet deep, tapering and rounded at 
its lower end, is made of cheesecloth or bobinet (not 
mosquito-netting, which is too frail), attached to a ring, one 
foot in diameter, of No. 3 galvanized iron wire, which in 
turn is fitted into a light wooden or cane handle about 
three and a half feet long. 

The killing-bottle (fig. 169) is prepared by putting a few 
small lumps (about a teaspoonful) of cyanide of potassium 



464 APPENDIX 111 

into the bottom of a wide-mouthed bottle holding about 
four ounces, and covering this cyanide with wet plaster of 
Paris. When the plaster sets it will hold the cyanide in 
place, and allow the fumes given off by its gradual 
volatilization to fill the bottle. Insects dropped into 
it will be killed in from two or three to ten minutes. 
Keep a little tissue paper in the bottle to soak up moisture 
and to prevent the specimens from rubbing. Also keep 
the bottle well corked. Label it ' 4 Poison," and do not 
breathe the fumes (hydrocyanic gas). Insects may be left 
in it over night without injury to them. 

Butterflies or dragon-flies too large to drop into the 
killing-bottle may be killed by dropping a little chloro- 
form or benzine on a piece of cotton, to be placed in a 
tight box with them. Larvae (caterpillars, grubs, etc.) 
and pupae (chrysalids) should be dropped into the vials of 
alcohol. 

In collecting, visit flowers, sweep the net back and 
forth over the small flowers and grasses of meadows and 
pastures, look under stones, break up old logs and stumps, 
poke about decaying matter, jar and shake small trees 
and shrubs, and visit ponds and streams. Many insects 
can be collected in summer at night about electric lights, 
or a lamp by an open window. 

When the insects are brought home or to the school- 
room they must be " pinned up. ' Buy insect-pins, long, 
slender, small-headed, sharp-pointed pins, of a dealer in 
naturalists' supplies (see p. 453). These pins cost ten 
cents a hundred. Order Klaeger pins, No. 3, or Carls- 
baeder pins, No. 5. These are the most useful sizes. 
For larger pins order Klaeger No. 5 (Carlsbaeder No. 8) ; 
for smaller order Klaeger No. 1 (Carlsbaeder No. 2). 
Pin each insect straight down through the thorax (fig. 170) 
(except beetles, which pin through the right wing-cover 
near the middle of the body). On each pin below the 



REARING ANIMALS AND MAKING COLLECTIONS 465 

insect place a small label with date and locality of capture. 
Insects too small to be pinned may be gummed on to 
small slips of cardboard, which should be then pinned up. 
Keep the insects in drawers or boxes lined on the bottom 
with a thin layer of cork, or pith of some kind. (Corn- 
pith can be used; also in the West, the pith of the flower- 
ing stalk of the century plant.) The cheapest insect- 
boxes and very good ones, too, are cigar-boxes. But 




Fig. 170. — Insect properly "pinned up." (From Jenkins and Kellogg.) 

unless well looked after they let in tiny live insects which 
feed on the dead specimens. For a permanent collection, 
therefore, it will be necessary to have made some tight 
boxes or drawers. Glass-topped ones are best, so that 
the specimens may be examined without opening them. 
A ' ' moth-ball ' (naphthaline) fastened in one corner of 
the box will help keep out the marauding insects. 

Butterflies, dragon-flies, and other larger and beautiful- 
winged insects should be " spread," that is, should be 
allowed to dry with wings expanded. To do this spread- 
ing- or setting-boards (figs. 171 and 172) are necessary. 
Such a board consists of two strips of wood fastened a short 
distance apart so as to leave between them a groove for 
the body of the insect, and upon which the wings are held 
in position until the insect is dry. A narrow strip of pith 
or cork should be fastened to the lower side of the two 



4 66 



APPENDIX III 



strips of wood, closing the groove below. Into this cork 
is thrust the pin on which the insect is mounted. An- 
other strip of wood is fastened to the lower sides of the 
cleats to which the two strips are nailed. This serves 

as a bottom and protects 
the points of the pins which 
project through the piece of 
cork. The wings are held 
down, after having been out- 
spread with the hinder mar- 
gins of the fore wings about 
at right angles to the body, 
by strips of paper pinned 
down over them. 

4 ' Soft specimens ' ' such as 
insect larvae, myriapods, and 
spiders should be preserved 
in bottles of alcohol (85 per 
cent). Nests, galls, stems, 
and leaves partly eaten by 
insects, and other dry speci- 
mens can be kept in small 
pasteboard boxes. 

For a good and full ac- 
count of insect-collecting and 
preserving, with directions 
for making insect-cases, etc . , 
see Comstock's " Insect 
Life," pp. 284-314. 

Birds. — In collecting 
birds, shooting is chiefly to be relied on. Use dust-shot 
(the smallest shot made) in small loads. For shooting 
small birds it is extremely desirable to have an auxiliary 
barrel of much smaller bore than the usual shotgun which 
can be fitted into one of the regular gun-barrels. In such 




Fig. 171. — Setting-board with butter- 
flies properly "spread." (After 
Comstock. ) 



REARING ANIMALS AND MAKING COLLECTIONS 467 

an auxiliary barrel use 32-calibre shells loaded with dust- 
shot instead of bullets. Plug up the throat and vent of 
shot birds with cotton, and thrust each bird head down- 
ward into a cornucopia of paper. This will keep the 
feathers unsoiled and smooth. 

Birds should be skinned soon after bringing home, after 
they have become relaxed, but before evidences of decom- 
position are manifest. The tools and materials necessary 
to make skins are scalpel, strong sharp-pointed scissors, 




jr IG . 172.— Setting-board in cross-section to show construction. (After 

Corn-stock.) 

bone-cutters, forceps, corn-meal, a mixture of two parts 
white arsenic and one part powdered alum, cotton, and 
metric-system measure. Before skinning, the bird should 
be measured. With a metric-system measure carefully 
take the alar extent, i.e. spread from tip to tip of out- 
stretched wings; length of wing, i.e. length from wrist- 
joint to tip ; length of bill in straight line from base (on 
dorsal aspect) to tip; length of tarsus, and length of 
middle toe and claw. 

To skin the bird, cut from anus to point of breast-bone 
-through the skin only. Work skin away on each side to 
legs ; push each leg up, cut off at knee-joint, skin down 
to next joint, remove all flesh from bone, and pull leg 
back into place; loosen skin at base of tail, cut through 
vertebral column at last joint, being careful not to cut 



468 APPENDIX III 

through bases of tail-feathers ; work skin forward, turning 
it inside out, loosening it carefully all around, without 
stretching, to wings; cut off wings at elbow-joint, skin 
down to next joint and remove flesh from wing-bones ; 
push skin forward to base of skull, and if skull is not too 
large (it is in ducks, woodpeckers, and some other birds), 
on over it to ears and eyes ; be very careful in loosening 
the membrane of ears and in cutting nictitating membrane 
of eyes ; do not cut into eyeball ; remove eyeballs without 
breaking; cut off base of skull, and scoop out brain; 
remove flesh from skull, and " poison " the skin by dust- 
ing it thoroughly with the powdered arsenic and alum 
mixture. Turn skin right side out, and clean off fresh 
blood-stains by soaking them up with corn-meal; wash 
off dried blood with water, and dry with corn-meal. 
Corn-meal may be used during skinning to soak up blood 
and grease. 

There remains to stuff the skin. Fill orbits of eyes with 
cotton (this can be advantageously done before skin is 
reversed) ; thrust into neck a moderately compact, elastic, 
smooth roll of cotton about thickness of the natural neck; 
make a loose oval ball of size and general shape of bird's 
body and put into body-cavity with anterior end under 
the posterior end of neck-roll ; pull two edges of abdominal 
incision together over the cotton, fasten, if necessary, 
with a single stitch of thread, smooth feathers, fold wings 
in natural position, wrap skin, not tightly, in thin sheet 
of cotton (opportunity for delicate handling here) and put 
away in a drawer or box to dry. Before putting away tie 
label to leg, giving date and locality of capture, sex and 
measurements of bird, and name of collector. Before 
bird is put into permanent collection it should be labelled 
with its common and scientific name. 

The mounting of birds in lifelike shape and attitude is 
hard to do successfully; and a collection of mounted birds 



REARING ANIMALS AND MAKING COLLECTIONS 469 

demands much more room and more expensive cabinets 
than one of skins. For instructions for the mounting of 
birds see Davie's 44 Methods in the Art of Taxidermy,'' 
pp. 39-57; or Hornaday's " Taxidermy and Zoological 
Collecting." For a more detailed account of making 
bird-skins, see also these books, or Ridgway's "Direc- 
tions for Collecting Birds." 

In collecting birds' nests cut off the branch or branches 
on which the nest is placed a few inches above and below 
the nest, leaving it in its natural position. Ground-nests 
should have the section of the sod on which they are 
placed taken up and preserved with them. If the inner 
lining of the nest consists of feathers or fur put in a 
1 ' moth-ball (naphthaline). 

To preserve birds' eggs they should be emptied through 
a single small hole on one side by blowing. Prick a 
hole with a needle and enlarge with an egg-drill (obtain 
of dealers in naturalists' supplies, see p. 453.) Blow with 
a simple bent blowpipe with point smaller than the hole. 
After removing contents clean by blowing in a little 
water, and blowing it out again. After cleaning, place 
the egg, hole downward, on a layer of corn-meal to dry. 
Label each egg by writing on it near the hole a number. 
Use a soft pencil for writing. This number should refer 
to a record (book) under similar number, or to an ki egg- 
blank," containing the following data: name of bird, 
number of eggs in set, date and locality, name of col- 
lector, and an}' special information about the eggs or nest 
which the collector may think advisable. The eggs may 
be kept in drawers or boxes lined with cotton, and di- 
vided into little compartments. 

For detailed directions for collecting and preserving 
birds' eggs and nests, see Bendire's " Directions for Col- 
lecting, Preparing, and Preserving Birds' Eggs and 



47° APPENDIX III 

Nests " or Davie's " Methods in the Art of Taxidermy, " 

PP- 74-78. 

* Mammals. — Any mammal intended for a scientific 
specimen should be measured in the flesh, before skinning, 
and as soon after death as practicable, when the muscles 
are still flexible. (This is particularly true of larger 
species, such as foxes, wildcats, etc.) The measure- 
ments are taken in millimetres, a rule or steel tape being 
used. (1) Total length: stretch the animal on its back 
along the rule or tape and measure from the tip of the 
nose (head extended as far as possible) to the tip of the 
fleshy part of tail (not to end of hairs). (2) Tail: bend 
tail at right angles from body backward and place end of 
ruler in the angle, holding the tail taut against the ruler. 
Measure only to tip of flesh (make this measurement with 
a pair of dividers). (3) Hind foot: place sole of foot flat 
on ruler and measure from heel to tip of longest toe-nail 
(in certain small mammals it is necessary to use dividers 
for accuracy). The measurements should be entered on 
the label, along with such necessary data as sex, locality, 
date, and collector's name. 

Skin a mammal as soon after death as possible. Lay 
mammal on back and with scissors or scalpel open the 
skin along belly from about midway between fore and hind 
legs to vent, taking care not to cut muscles of abdomen. 
Skin down on either side of the body by working the skin 
from flesh with fingers till hind legs appear. Use corn- 
meal to stanch blood or moisture. With left hand grasp 
a leg and work the knee from without into the opening 
just made; cut the bone at the knee, skin leg to heel and 
clean meat off the bone (leaving it attached of course to 
foot). In animals larger than squirrels skin down to tips 

* The following directions for making skins of mammals were written 
for this book by Mr. W. K. Fisher of Stanford University, an experienced 
collector. 



REARING ANIMALS AND MAKING COLLECTIONS 47 X 

of toes. Do the same with other leg. Skin around base 
of tail till the skin is free all around so that a grip can be 
secured on body; then with thumb and forefinger hold the 
skin tight at base of tail and slowly pull out the tail. In 
small mammals this can be done readily, but in foxes it 
is often necessary to split the skin up along the under side 
and dissect it off the tail-bones. After the tail is free 
t kin down the body, using the fingers (except in large 
mammals) till the fore legs are reached; treat the fore legs 
iii the same manner as hind legs, thrusting elbow out of 
the skin much as a person would do in taking off a coat; 
cut bone at elbow; clean fore-arm bone. Skin over neck 
to base of ears. With scalpel cut through ears close to 
skull. With scalpel dissect off skin over the head (taking 
care not to injure eyelids) down to tip of nose, severing 
its cartilage and hence freeing skin from body. Sew 
mouth by passing needle through under lip and then across 
through two sides of the upper lip; draw taut and tie 
thread. Poison skin thoroughly. Turn skin right side 
out. Next sever the skull carefully from body, just where 
the last neck-vertebra joins the back of the skull. It is 
necessary to keep the skull, because characters of bone and 
teeth are much used in classification. Remove superfluous 
meat from the skull and take out brain with a little spoon 
made of a piece of wire with loop at end. Tag the skull 
with a number corresponding to that on skin, and hang 
up to dry. A finished specimen skull is made by boiling 
it a short time and picking the meat off with forceps, 
further cleaning it with an old tooth-brush, when it is 
placed in the sun to bleach. Care must be taken always 
not to injure bones or dislodge teeth. 

Mammals are stuffed with cotton or tow; the latter is 
used in species from a gray squirrel up. Large mammals 
stuffed with cotton do not dry readily, and often spoil. 
Being much thicker-skinned than birds, mammals require 



47 2 APPENDIX 111 

more care in drying and ordinarily require a much longer 
period. Soft hay may be substituted for tow; never use 
feathers or hair. Roll a longish wad of cotton about the 
size of body and insert with forceps, taking care to form 
the head nearly as in life. Split the back end of the cot- 
ton and stuff each hind leg with the two branches thus 
formed. Roll a piece of cotton around end of forceps 
and stuff fore legs. Place a stout straight piece of wire 
in the tail, wrapping it slightly to give the tail the plump 
appearance of life. (If the cotton cannot be reeled on to 
the wire evenly, leave it off entirely.) Make the wire 
long enough to extend half way up belly. Sew up slit in 
belly. Lay mammal on belly and pin out on a board 
by legs, with the fore legs close beside head, and hind 
legs parallel behind, soles downward. Be sure the label 
is tied securely on right hind leg. 

For directions for preparing and mounting skeletons of 
birds, mammals, and other vertebrates, see the books of 
Davie and Hornaday already referred to. 

Fishes, batrachians, reptiles, and other animals. — The 
most convenient and usual way of preserving the other 
vertebrates (not birds or mammals) is to put the whole 
body into 85 per cent alcohol or 4 per cent formalin. 
Batrachians should be kept in alcohol not exceeding 60 
per cent strength. Several incisions should always be 
made in the body, at least one of which should penetrate 
the abdominal cavity. Anatomical preparations are simi- 
larly preserved. By keeping the specimens in glass jars 
they may be examined without removal. Fishes should 
not be kept in formalin more than a few months, as they 
absorb water, swell, and grow fragile. 

Of the invertebrates all, except the insects, are pre- 
served in alcohol or formalin. The shells of molluscs 
can be preserved dry, of course, in drawers or boxes 
divided into small compartments. 



INDEX 



j^*=" Illustrations are indicated by ar asterisk 



A cant hi a lectularia, *i88. 

Acarina, 230. 

Acmara speetoraai, "^248. 

Actinozoa, 97, 102. 

Adaptation, 407. 

Adder, spreading. 321. 

jfEgialitis voci/era, 349. 

Agalenidae, 235. 

A^kistrodon piscivorous, 323. 

Aix s pons a, 347. 

Albatross, 346. 

Aha impennis. 345. 

Alee americana, ^385. 396. 

Alligator, 326. 

Alligator mississippensis, 326. 

Alternation of generations, 96. 

Amblophtes rupestris, 282. 

Amblysloma. 297, 298. 

Ambly stoma aiaculatiun, 299. 

Ameuirus. 282. 

Amoeba, *32; structure and life of, 

Amphioxus, 278. 

Anaconda, 324. 

Anas bosehas. 347. 

Anatomy defined. 3. 

Anguiila, 284. 

Angitittula. 140. 

Anolis principalis, 319. 

Anosia plexippas. anatomy of larva 
of. 177, external structure of. 171, 
*I72; life of. 175; mimicked by 
Basilar ckia archippus, ^433. 

Anseres. 347. 

Ant. little black, ^224; little brown. 
223. 

Antelope. ^395, 396. 

Antenna of carrion beetle. ^184. 

Antilocapra americana, *395- 396. 

Antrostomus vociferns, 356. 



Ant, 212. 21S. 223. 

Anura, 299. 

Ape. 401. 

Aphidiae, 200. 

Apis Jtorea, comb ot. *222. 

Apis mellijiea. -2 18. 

Appearance, terrifying, 430. 

Aquarium, 457. 

Aquarium, battery-jar, ^461. 

Aquila chryscctos. 342. 

Arachnida. 144. 229. 

Aretomys monax. 391. 

Ardea herodias. 358. 

Ardea viresce>is. 347. 

Argiope sp., ^236. 

Argonaut, 257. 

Argonaut a argo. 257. 

Ariolimax californica^ ^252. 

Arthbgastra, 230. 

Arthropoda, 144. 

Ascidian, 259. -261. 

Aspidiotus aurantii. -198. 

Asterias sp.. structure and life of. 

108. 
Asterias. *log ; cross - section of, 

*II2. 

Asterias oeraeia, *s.22. 
Aster ina mineata. *I22. 
Asteroidea. 120, 121. 
Attidce. 235. 
Auk. great. 345. 
Aves, 327. 

Av thy a vallisneria. 347. 
Ayu. 28?. 



Back -swimmer, 
Balanus. *•■ 



197. 199. 



i53- 
Balcena glaeialis. 393. 

Bahena mysticetus. 393, 

Barbadoes earth, 82. 



473 



474 



INDEX 



349- 



or, 32 


1. 




body 

classi 

and 


form 
fixation 
habits 


and 
of, 
of, 


292. 







Barnacle, *I53, 155; sessile, 155; 
stalked, 155. 

Barn-owl, 353. 

Bartramia longicauda, 

Bascanhim constrictor, 

Bass, 282. 

Bat, hoary, ^392. 

Batrachia, 291. 

Batrachians, 291 ; 
structure of, 292 ; 
295 ; life-history 
295 ; structure of, 

Bat, 391. 

Bead-snake, 322. 

Bear, 398. 

Beaver, 391. 

Bed-bug, *i88. 

Bee, 212; solitary, 216. 

Beetle, great water-scavenger, 163; 
external structure, *i64 ; inter- 
nal structure, ^167; antenna of 
carrion, *i84; Colorado potato. 
209. 

Beetle, 206; carrion, 209; whirligig, 
206. 

Bell -animalcule, structure and life 
of, 75. 

Bills of birds, 362. 

Bipinnaria, 119. 

Bird, frigate, 346 ; man-of-war, 
346; outline of body showing ex- 
ternal regions, *330; ruby-throat 
humming, nest and eggs of, 

*357- 

Bird-louse, ^194. 

Birds, 327; bills and feet of, 362; 
body form and structure of, 336; 
care of young, 366; classification 
of, 340; collecting, 466; determin- 
ing, 359; development and life- 
history of, 339; feeding habits of, 
370 ; flight and songs of, 364 ; 
migration of, 367 ; molting of, 361 ; 
nesting of 366; protection of, 370. 

Bird-skins, making, 466. 

Bison bison, 396, *397- 

Bittern, 348. 

Blacksnake, 321. 

Blissus leucopterits, 198. 

Blood, circulation of, in mammal, 
*376. 

Blood of toad, structure of, 40. 

Blow-fly, 201 t 202; section through 
compound eye of, ^185. 

i; Bob Jordan " (monkey), :: 400. 



Bobwhite, 350. 

Bo nib us, 216. 

Bombyx mori, anatomy of larva of, 

*I78. 
Bonasa twibellus, 350. 
Books, reference, 454. 
Borer, peach-tree, *2io. 
Botaurus lentiginosis, 348. 
Box tortoise, 315. 
Brachynotus nndus, ^153. 
Brains of vertebrates, ^378. 
Branch, defined, 73. 
Branta canadensis, 347. 
Breeding cage, 458, 459. 
Brittle-stars, 120, 121, 122. 
Bubo virginianns, 353. 
Buffalo, 396, *397. 
Bufo lentiginosis, 301 ; dissection 

of, 5- 

Bullfrog, 299. 

Bumblebee, 216. 

Bunodes caliJor7iica, 103. 

Buteo, 353. 

Butterfly, external structure of, 171, 
^172 ; life of, 175 ; monarch, 
anatomy of larva of, 177 ; dead 
leaf, ^429; mimicked by viceroy, 

*433- 

Butterflies, 205; setting-board for, 
*4o6, 4 6 7 . 

Buzzard, turkey, 352. 

Cachalot, 393. 

Cage, lamp-chimney and flower-pot 
breeding, *459; soap-box breed- 
ing, *45 8 - 

Cake-urchin, 124. 

Calcarea, 91. 

Calliphora voj?iitoria, 202 ; section 
through compound eye of, *i85. 

Callorhinus alascanus, *399- 

Callorhinus ursim/s, parasitized, 

*422. 

Cambarus sp., dissection of, 18; life 

of, 146. 
Camphephilus principalis , 355. 
Ca7icer productus, * 1 53 . 
Cam's familiaris, 3 98. 
Cam's latrans, 398. 
Canis nubilus, 398. 
Canvas-ba.ck, 347. 
Carcharcdon, 280. 
Caribou, 396. 
Cassowary, 343. 
Castor canadensis, 39 1. 



INDEX 



475 



Caterpillar, apple tent. 208; forest 
tent, 209. 

Catfish. 282. 

Cat hart es aura. 352. 

Caz'ia, 390. 

Cell, defined, 37. 

Cell differentiation, degrees of, 54. 

Cell products, 38. 

Cell wall, 38. 

Centiped, *228, 229; skein, ^228. 

Centipeds, 226. 

Centrocercus urophasiamis. 350. 

Centrums sp., ^236. 

Cephalpoda, 246. 

Cercopithicus, *400. 

Cervus canadensis, *394. 395. 

Ceryle at cyan, 354. 

Cete, 393. 

Cetorhinus, 270, 280. 

Ch ictura pelagica . 356. 

Chain-snake, 320. 

Chalk, 81. 

Chameleon, green, 318. 

Chelonia. 313, 314. 

Che Ionia my das. 315. 

Chelydra serpentina. 314. 

Chen hyper borea, 247. 

Chicken-hawk, 353. 

Chimney-swift, 356. 

Chinch bug, 198. 

Chipmunk, 391. 

Chiroptera, 391. 

Chitin, 145, 158. 

Chlorostomnm funebrale. ^248. 

Chordata, 259; classification of. 260. 

Chordeiies virginianus, 356. 

Chroma top hore. 256. 

Chub, 282. 

Chryseniys, 314. 

Cicada, 199 ; seventeen-year. -200; 
septendecim, *200. 197. 

Circulation of blood in mammal, 
* 37 6. 

Circus huds 07ii its. 352. 

Cistudo Carolina, 314. 

Clams, 246; hard shell, 247; soft- 
shell, 247. 

Class, defined, 7^5. 

Classification, basis and signification 
of, 65; denned. 3; example of, 68. 

Clisiocampa americana. larvae, *2o8. 

Clisiocampa disstria. caterpillars, 
*2C>9; life-history ot, 207. 

Clupea harengus, 284. 

Cobra-da-capello, 314. 



Coccidae, 198. 

Coccyges, 354. 

Coccyzus, 354. 

Cock, chapparal, 354. 

Cockroach. 192. 

Codfish, 284. 

Ccecilians, 302. 

Ccelenterata, 92; classification of, 
96 ; development and life-history 
of, 95 ; form of, 93 ; skeleton of, 
95 ; structure of, 94. 

Colaptes auratus. "355. 

Co/apt es caper, 355. 

Coleoptera, 206. 

Colin us virginianus, 350. 

Collections, making, 461, 

Color, use of, 424. 

Colors, warning. 430. 

Colubrid.e, 319. 

Columba fas data, 351. 

Columba Hvia, 351. 

Columbae, 351. 

Colymbus auritus. 343. 

Comb-building of honey-bee, *22i. 

Comb of East Indian honey-bee, 

*222. 

Commensalism, 155, 413. 
Communal life, 411. 
Condor, California, 352. 
Condylura cristata, 391. 
Conjugation. 35. 60. 
Conotrachelus craiccgi, *2I2, 213. 
Conotrache/us nenuphar, ^214. 
Constrictor, boa, 324. 
Conurus carolincnsis, 353. 
Coot, American, 349. 
Copperhead, 322. 
Coral, 95; branching, *ic>4; red, 

106. 
Coral islands, 104, 106. 
Coral polyps, 104. 
Coral reefs, 106. 
Corals, 92, 102, 104. 
Coregonus, 283. 
Corisa, 197. 
Cor is a sp.. ^199. 
Cormorant, 346. 

Cornea of eye of horse-fly, *i86. 
Cottontail, 390. 
Coyote, 398. 

Crab. 151, 152; soft-shelled, 154. 
Crabs, ^153. 

Crane, sand-hill. 348; whooping, 348. 
Crayfish, dissection of, 18, *i8, 22; 

life of, 146. 



476 



INDEX 



Cricket, house, ^193. 

Cricket, 192. 

Crinoid, *i26. 

Crinoidea, 121, 125. 

Crocodile, 326. 

Crocodilea, 313, 325. 

Crocodilus mhericanus, 326. 

Crotalus, 322. 

Crustacea, 144, 146 ; form and 

structure of, 147. 
Cryptobranchus, 298. 
Ctenophora, 97, 107. 
Cuckoos, 354. 
Cucuinaria, 124. 
Cucumber-beetles, 209. 
Culex sp., 204, *2C>5. 
Curculio plum, ^214. 
Curculio quince, *2i2, 213. 
Curlew, long-billed, 350. 
Cuttlefishes, 255. 
Cyclas, 247. 
Cydophis cestivus, 320. 
Cyclops, 148, *I49- 
Cyclostomata, 278. 
Cytoplasm, 38. 

Dabchick, 343. 

Dactylus sp., ^249. 

Damp bug, *i5i. 

Darters, 282. 

Dasyatis, 281. 

Decapoda, 151. 

Decapods, 256. 

Deer, 396. 

Degeneration, 417. 

Dendrostomium cronjhelmi, ^134. 

Development, defined, 3 ; embry- 
onic, defined, 62; post-embryonic, 
defined, 62; simplest, 59. 

Diapheromera fe?norata, ^427. 

Diaspis rosce, *I98. 

Dictynidse, 235. 

Didelphis virginiana, 390. 

Diemy 'stylus torosus, ^299. 

Diemy stylus viridescens, 297. 

Dimorphism, 96. 

Diptera, 201. 

Distribution, barriers to, 437; geo- 
graphical, 435 ; laws of, 436 ; 
local, of birds, 367; modes of, 437. 

Diver, great northern, 343. 

Dolphins, 393. 

Doris tuber cu lata, ^254. 

Draco, 319. 

Dragon-flies, 294. 



Dragon-fly, *ig6. 
Dragon, flying, 318. 
Drawings, 447. 
Djyobates pubescens, 355. 
Dry bates villas us, 355. 
Duck, ruddy, 347. 
Dyttcus sp., 210. 
Dytiscidse, 207. 

Eagle, bald, 352; golden, 352. 

Ear of locust, ^187. 

Earthworm, anatomy of, *I26 ; ali- 
mentary canal of, *I26 ; cross- 
section of, ^131 ; reproductive 
organs of, ^130; structure and life 
of. 127. 

Earthworms, 136. 

Echinoderm, development of, 119 ; 
structure of, 117; shape of, 116. 

Echinodermata, 108 ; classification 
of, 120. 

Echinodoris sp., ^254. 

Echinoidea, 121, 122, 123. 

Eciton, 225. 

Ecology, animal, 403. 

Ectopistes migratorius, 351. 

Eel, 284. 

Eft, green, 297; western brown, 
*299- 

Eggs of birds, collecting, 469. 

Eider, 347. 

Elasmobranchii, 279. 

Etas soma, 271. 

Elk, *394, 396. 

Epeiridae, 236. 

Ephemerida, 194. 

Epialtus productus, ^153. 

Equipment of laboratory, 450. 

Equipment of pupil, 447. 

Erethizoii dorsatus, 391. 

Erethizon epixanthus, 391. 

Eretmochelys Unbricata, 215. 

Erismatura rubida, 347. 

Eumeces skeltonianus, ^316. 

Eupomotic gibbosuc, dissection of, 
(facing) ^263; life of, 270 ; struc- 
ture of, 263. 

Exocostus, 285. 

Eye, cornea of compound, of horse- 
fly, *i86 ; section through com- 
pound, of blow-fly, "^185. 

Eye of vertebrate, ^378. 

Ealco sparverius, 353. 
Family, defined, 72. 



INDEX 



477 



Fauna, 440. 

Feather-stars, 121, 125, *I26. 

Feet of birds, 362. 

Felis conco/or f 398. 

Ferae. 397. 

Fever, yellow, and mosquitoes, 205. 

Fiber zibet hie us , 391. 

Fire-flies, 209. 

J ishes, 263; body form and struc- 
ture of, 271 ; classification of, 277; 
development and life-history of, 
276; habits and adaptations of, 

285. 

Fish-hatcheries, 288. 

Flat-worms, 137. 

Flea, house, ^204. 

Flickers, 355. 

Flies, 201; chaicid, 214; ichneumon, 

212. 
Flight of birds, 366. 
Flying fishes, 285. 
Food-fishes, 288. 
Food of birds, 370. 
Foraminifera, 80. 
Fox, 398. 

Fregata aquila, 346. 
Frogs, 299. 

Fuliea americana, 349. 
Fulmars, 345. 
Function, defined. 14. 
Functions, essential, 15. 
Fur-seals, 398, ^399. 
Fur-seals, parasitized, *422 e 

Gadus ea Marias, 284. 

Galley-worm, ^227. 

Gall-flies, 214. 

Gallinae, 350. 

Gastropoda, 246. 

Gavia imber, 347. 

Gavial, 326. 

Generation, spontaneous ; 58. 

Genmules, 85. 

Genus, defined. 70. 

Geococcyx calif ornianus, 354. 

Gephyrean, ^134. 

Girdler, currant stem, ^'215. 

Glass-snake, 317. 

Glires, 391. 

Goat, Rocky Mt., 397. 

Gonionema vertens, *ioi. 

Goose, Canada, 347. 

Gophers, pocket, 391. 

Gordius, 140. 

Grant ia, *4J. 



Grand a sp., 85. 

Grayling. 284, 

Grebe, horned, 343 ; pied-billed, 

343- 
Green, methyl, 351. 
Greensnake, 320. 
Gregariousness, 410. 
Grouse, ruffed. 350. 
Grits americana, 348. 
Grits mexicana, 348. 
Guillemot. 345. 
Guinea-pig, 391. 
Guinea- worm, 140. 
Gull, great black- backed, 345. 
Gulls, 345. 
Gymnophiona, 302. 
Gyrinidae, 206. 

Habitat, 441. 

Hag-fishes, 279. 

Hair-worms, 140. 

Ha licet us leucocephalus , 352. 

Halictus y 216. 

Harporhynckus redivivus, *37I. 

Hatteria, 312. 

Hawk, marsh, 352. 

Helmet shells, 255. 

H Jo derma horridum, "317. 

Hemiptera, 197. 

Hermit-crab, 154. "^153. 

Herodiones, 347. 

Heron, great blue, 348 ; green, 347. 

Herring, 284. 

Heteredon platirhinos, 321. 

Hippocampus hippocampus, "285. 

Holothuroidea, 121, 124. 

Homo sapiens, 398. 

Honey-bee, *2i8 ; brood-cells of. 
^219; building comb, *22i; comb 
of East Indian, *222; cross-sec- 
tion of body of pupa of, ^191. 

Honey-bees, 212. 

Honey-dew, food of ants, 223. 

Hornets, 217. 

Horse-fly, cornea of eye of, *i86 

House-fly, 202. 

Humming-birds. 356. 

Hydra, ^47 ; structure and life of, 46. 

Hydrozoa, 96, 97. 

Hydrophilidae, 207. 

Hydrophilus sp., external structure 
of, *i64 ; internal structure of, 
*i67. 
Hygrotrechus, 198. *I99- 
Hyia pickeringii, 300. 



478 



INDEX 



Hyla versicolor, 300. 
Hymenoptera, 212. 
Hyptiotes sp., and web, ^238. 

Iguana, 318. 

Imago, 190. 

Injecting-masses, 451. 

Insect, pinned, "^465; twig, ^427; 
wingless, *i8i. 

Insecta, 157. 

Insectivora, 391. 

Insects, classification of, 191 ; col- 
lecting, 463; communal, 215; de- 
velopment and life- history of, 188; 
form and structure of, 181 ; killing- 
bottle for, *463; social, 215. 

Invertebrate, defined, 30. 

Islands, coral, 104, 106. 

Isopod, *I5I. 

Isopoda, 150. 

Jack rabbit, 390. 
jfanus integer, *2I5» 
Jellyfish, *ioi. 
Jelly fishes, 92; colonial, 97. 
Joint-snake, 318. 
Julus, *327. 
June-beetle, 212. 
June-beetles, 206. 

Kaliima, *<\2Q. 

Kangaroo, 389. 

Katydids, 192. 

Kelp-crab, ^152. 

Kill-deer, 349. 

Killing-bottle for insects, *463. 

Kingfisher, belted, 354. 

Laboratory, equipment of, 450. 
Lacknosierna, 212. 
Lady-birds, 209. 
Lagopus, 350. 
Lake-lamprey, 279. 
Lampetra wilderi, 279. 
Lamprey, ^278; brook, 279. 
Lampropeltis boy Hi, *32i. 
Lampropellis getulus, 320. 
Lancelet, 278. 
Larks, horned, ^358. 
Larns marinus, 345. 
Larva, 189; of Monarch butterfly, 
anatomy of, 177 ; parasitized, 

*420. 

Lasiurus borealis, 392. 
Lasiurus cinereus, ^392. 



Lasius jlavus, 223. 

Leeches, 136. 

Lemurs, 401. 

Leucania unipuncta, *2ii. 

Lepidocyrtus americanus, *i8i. 

Lepidoptera, 205. 

Leptocardii, 277. 

Leptoplana calif ornica, *I38. . 

Lepus campestris, 390. 

Lepus nuttali, 390. 

Life-history, defined, 62. 

Life-processes, essential, 15. 

LimicolcE, 349. 

Limpets, 255, ^248. 

Lit tor in a scutulata, *248. 

Live cages, 457. 

Liver of toad, structure of, 41. 

Lizard, ^309. 

Lizards, 316. 

Lobster, 151, 152. 

Locust, differential, 156 ; ear of, 
*i87 ; red-legged, 156, *I57 ; 
Rocky Mt, 156; structure and life 
of, 156; two- striped, 156. 

Locusts, 192. 

Loligo, 257. 

Longipennes, 345. 

Loon, 343. 

Lumbricus sp., alimentary canal of, 
* 13 1; cross- section of, ^132; struc- 
ture and life of, 127. 

Lung-fish, 285. 

Lycena, scales of wings of, *2o6. 

Lycosidae, 235. 

Lynx rufus, 398. 

Macrocheira, 154. 

Madrepora cervicornis, ^105. 

Malacleminys palustris, 3 1 4. 

Malaria and mosquitoes, 105. 

Mallard, 347. 

Mammal, circulation of blood in. 
* 37 6. 

Mammalia, 373. 

Mammals, 373 ; body form and 
structure of, 381 ; classification of, 
389; development and life-history 
of, 388; habits, instinct and rea- 
son of, 388 ; making skins of, 
470. 

Man, 398. 

Man-of-war, Portuguese, 98, *97< 

Marsupialia, 389. 

Martesia xylopkaga, *25i = 

Mahsasau^a, 32. 



INDEX 



479 



May-flies, 194. 

May-fly, nymph of, ^197. 

Medusa. *ioi. 

Megalobatrachus, 298. 

Megascops asio. *352, 353. 

Melanerpes erythrocephalus, 355. 

Melanerpes formicivorus. 356. 

Melanophts sp., ear of, ^187; struc- 
ture and life-history of. 157. 

Melanoplus vibittattis, 157. 

Melanoplus differentialis, 157. 

Melanoplus femur- rubrum, 157, * 158. 

Melanoplus sprettis, 157. 

Meleagrina margaritifera, 250. 

Merula migratoria propinqua, *368. 

Metamorphosis, complete, 171, 188. 
189; incomplete, 171, 189. 

Metazoa, defined, 43. 

Mice. 391. 

Micropterus dolomien, 282. 

Micropterus salmoides, 282. 

Migration of birds, 367. 

Mimicry, 430. 

Millipeds, 226. 

Mite, cheese, ^230. 

Mites, 229. 

Modifications of structure and func- 
tion, 29. 

Moles, 391. 

Mollusca, 239. 

Molluscs, 239; classification of, 246; 
development of, 246 ; form and 
structure of, 245. 

Molting, 361; of birds, 361. 

Monitor, 318. 

Monkey, *400. 

Momomerium minutum, "224. 

Monster, Gila, ^317. 

Moose, ^385, 396. 

Morphology, defined. 3. . 

Mosquito, 202, *203. 

Mosquitoes, 201 ; and malaria, 205 ; 
and yellow fever, 205. 

Moth, forest tent-caterpillar, life- 
history of, *2C>7. 

Moths, 205. 

Mourning dove, 351. 

Mouse, life-history and habits of, 
379; structure of, 373. 

Mud-eel, 297. 

Mud -hen, 349. 

Mud-puppies, 297. 

Mud-turtle, 313. 

Multiplication of one-celled animals, 
59; of many-celled animals, 6l. 



Murres, ^344. 

Muscles of toad, structure of. 41. 
Mus decumanus, 391. 
Mus musculus, structure of, 373. 
Mus rattus, 391. 
Musk-rat. 391. 

Mussel, fresh-water, life-history and 
habits of, 243; structure of, 

239- 
Mya arenaria^ 247. 
My otis subulatus, 392. 
Myriapoda. 144, 226. 
Mytilus calif ornianus, *248. 
Myxine, 279. 



Names, scientific, 68. 
Xarcobatis. 281. 
Natrix sipedon, 320. 
Nautilus, 255; pearly. 258. 
Nautilus po/npilius, 258. 
Necturus, 297. 298. 
Nemathelminthes, 140. 
Neotoma pennsylvanica, 391. 
Nereid, ^134. 
Nereis sp.. ^134. 
Nesting of birds, 366. 
Nest of oriole, "365. 
Net t ion carolinense. 347.] 
Night-hawk. 356. 
Night-heron. 348. 
Xirmus prccstans, *I94- 
Non-calcarea, 91. 
Notes. 447, 448. 
Notochord, 259. 
Xotonecta. 197, 199. 
Nucleus, 38. 

Nudibranchs, 252, "254. 
Numenius. longirostris, 350* 
Nyctea nyctea. 353. 
Nycticorax, 348. 

Octopi, 255. 

Octopods, 256. 

Odocoileus americauus, 396. 

Odonata, 194. 

Oligoch^etDe. 136. 

Olor, 347. 

Ommatostrephes califoruica. "^257. 

Oncorhynchus tschaivtsclia. 283. 

One-celled animals, multiplication 

of, 57. 
Ooze, foraminifera, 81 ; radiolaria, 

81. 



Opheosaurus vent ra lis. 317 



48o 



INDEX 



Ophiuroidea, 121, 122. 

Opossum, 389. 

Order, defined, 72. 

Oreamnos montanus, 397. 

Organ, defined, 14. 

Orthoptera, 192 ; sound-making of, 

193- 
Orb- web of Epeiridae, 236. 
Ostrea virginiana, 248. 
Ostriches, 341, *342. 
Otocoris alpestris, ^358. 
Chris canadensis, ^383, 396. 
Owl, burrowing, 353; great gray, 

353 ; g reat homed, 353 ; snowy, 

353- 
Oyster, 248. 
Oyster-crab, 154. 
Oyster-drills, 255. 
Oysters, 246; "seed" of, 249; 

" spat " of, 249. 

Pagurus samuelis, *I53« 

Paludicol3e, 348- 

Panther, 398. 

Paramecium, ^35; multiplication of, 
60; structure and life of, 34. 

Parasitism, 415. 

Paroquet, Carolina, 353. 

Parrots, 353. 

Passer domesticus, dissection of, (fac- 
ing) *327 ; life-history and habits 
°f> 335 i structure of, 327. 

Passeres, 357. 

Pearl-oyster, ^249. 

Pelecanus calif ornicns, 346. 

Pelecanus erythrorhynchus, 346. 

Pelecanus fuscus, 346. 

Pelecypoda, 246. 

Pelican, brown, 346; white, 346. 

Pentacrinus sp., ^126. 

Pent act a /rondos a, ^125. 

Peripatus eiseni, *226. 

Per la sp., *i82. 

Petrels, 345. 

Petromyzon marinus t ^278. 

1 halacrocorax, 346. 

Pheasants, 350. 

PJioca vitulina, 397. 

Phcebe, black, nest and eggs of, 
*34o. 

Pholas sp., ^250. 

Phrynosoma, 318. 

Phylloxera, grape, 198, 201. 

Phylloxera vastatrix, 198, 20 1. 

Phylum, defined, y^. 



Physalia sp., *9J. 

Physeter macrocephalus, 393. 

Physiology, defined, 3. 

Pici, 354. 

Pickerel- frog, 300. 

Pigeon, band-tailed, 351; passenger, 

351- 

Pinnotheres, 154. 

Pipe-fish, 285. 
Pisces, 263. 

Pituophis bellona, ^323. 
Planar ia sp., ^138. 
Planarian, fresh- water, *I38 ; ma- 
rine, *I38. 
Planarians, 137. 
Plant-lice, 197, 200. 
Planula, 96. 
Platyhelminthes, 137. 
Plectrophenax nivalis, ^358. 
Plethodon, 297. 
Plover, field, 349. 
Pluteus, 119. 

Podilymbus podiceps, 343. 
Poison-fangs of rattlesnake, *324. 
Pollicipes poly mentis, * 1 5 3 . 
Polymorphism, 96. 
Polynce brevisetosa, *I34- 
Polyps, 92, 97. 
Pomoxis annularis , 282. 
Pomoxis separoides, 282. 
Pond-snails, 252. 
Porcupine, 390. 
Porcupine-fish, 285. 
Porifera, 84. 
Porpoises, 393. 
Porzana Carolina, 349. 
Prairie-chicken, 350. 
Prawns, 152. 
Preparations, preserving anatomical, 

45 2 - ' 
Primates, 398. 
Pristis pectinatis, 281. 
Protophyta, 82. 
Protoplasm, described, 39. 
Protopterus, 288. 
Protozoa, defined, 43, 75; form of, 

78; marine, 80. 
Pseudemys, 313. 

Pseudogryphus califomianus, 352. 
Psittaci, 353. 
Ptarmigan, 356. 
Puff-adder, 325. 
Puffins, 345. 
]Hlex irritans, *2C4 
Pulmonata, 253, 



INDEX 



481 



Puma. 398. 

Pumpkin seed, life of. 270; structure 

of. 263. 
Pupa. 189; cruss-section of body of. 

of honey-bee. *I9I. 
Pupation. 189. 
Purpura saxicola, ^248. 
Pygopodes. 343- 
Python, 324. 

Quail 350. 

Querqueditla discors. 347. 

Rabbits, 390. 

Radiolaria, 80. 

Rai 1 , Carolina. 349. 

Raja er'uwcea, 280. ^281. 

Raja Icevis^ 281. 

Rana catesbiana. 299. 

Rana palustris. 300. 

Rana sylvatica, 300. 

Rangifer caribou, 396. 

Raptores. 351. 

Ratitae. 341. 

Rats, 391. 

Rattlesnake poison-fangs, ^324. 

Rattlesnakes, 321. 

Rattles of rattlesnake, ^223. 

Reefs, coral. 106. 

Reindeer, 396. 

Re mora, ^87. 

Remor apsis brachyptera, ^287. 

Root-cage. 460. 

Reptiles, budy form and organiza- 
tion of, 309; classification of. 312; 
life-history of, 312; structure of, 
310. 

Reptilia, 303. 

Resemblance, protective. 326. 

Rheas, 343. 

Road -runner, 354. 

Robber-ant. 225. 

Robin, Western, ^368. 

Rock-bass, 282. 

Rock-crab. ^153. 

Rock-dove, 35 [. 

Rodents, 390. 

Rosalina various, *8l. 

Rotifer^., *i43*. 

Round worms, 140. 

Ruminants, 395. 

Saccuiina, 67, ^418. 
Sage-hen. 350. 

Salamander, red-backed, 297; tiger, 
*292. 



Salamanders. 297. 

Salmo irideus. ^283. 

Salmon, king. 284. 

Sand-dollar, 124. 

Sand-pipers. 345. 

Sanninoidea ex/stiosa. *2 12. 

Sap-sucker, downy, 355; hairy, 355, 

Saw-fish, 281. 

Sayornis nigricans, nest and eggs 
of, *34C 

Scale insect, red-orange, ^198. 

Scale insects, 198. 

Scale rose, ^198. 

Scales of wings of Lyc?ena, *2o6 ; 
wing of Monarch butterfly, ^174. 

Scallops, 246. 

Sea lops aquaticus, 391. 

Scap/iiopus, 300. 

Sceloporus, 317. 

Sciuropterus voians, 391. 

Sciurus carolinensis, 39 1. 

Sciurus Ziudsouicus, 391. 

Sciurus ludovicianus, 391. 

Scolopendra sp.. 228, 229. 

Scorpion, ^230. 

Scorpions. 229. 

Scot i apt ex ciner a, 353. 

Screech-owl. ^35 2. 353. 

Scutigera forceps , *2 2 8. 

Scyphozoa, 97, 101. 

Sea anemones, 92. 102, ^103. 

Sea cucumber, ^125. 

Sea-cucumbers, 108, 121, 124. 

Sea-fan. 107. 

Sea-feather, 106. 

Sea-horse, -285. 

Sea-lamprey, 279. 

Sea-lily, 118. 

Sea-pen, 106. 

Sea-shells, 252. 

Sea-slugs. 255. 

Sea-snakes, 325. 

Sea-squirt. *26i. 

Sea-turtles. 315. 

Sea-urchin, *H4; structure of. 113. 

Sea-urchins, 108. 121, 123. 

Seals, 397. 

Selection, artificial. 409 ; natural, 
406. 

Sembling of insects, 176. 

Sepias, 256. 

Setting-board for butterflies, ^"466. 
467. 

Shark, basking, 270, 280; hammer- 
headed, 280; man-eating, 280, 



482 



INDEX 



Sharks, 280. 

Shearwaters, 345. 

Sheep-fluke, 138. 

Sheep. Rocky Mt., ^383, 397. 

Shipworm, 251. 

Shoveller, 347. 

Shrews, 391. 

Shrimp, 151, 152. 

Silk-worm, anatomy of, ^178. 

Siphonophore, 98. 

Siren, 297, 298. 

Sistrurus, 322. 

Skate, barn-door, 281 ; common, 280, 

*2'8l. 

Skates, 280. 
Skeleton of coral, 105. 
Skeletons, preparing, 452. 
Skink,' blue tailed, ^317. 
Skin of toad, structure of, 40. 
Slipper-animalcule, ^35 ; structure 

and life of, 34. 
Slug, giant yellow, *252. 
Slugs, 252, 253. 
Snake coral, 321. 
i Snake, garter, *32o; life of, 307; 

structure of, 303; gopher, *322. 
Snake king, *32i. 
Snakes, 316. 
Snails, 252, 253. 
Snapping-turtle, 314. 
Snipes, 349. 
Snowflakes, *358. 
Snow-goose, 347. 
Social life, 410. 
Somateria, 347. 
Songs of birds, 364. 
Sora, 349. 

Sound making of orthoptera, 193. 
Spadefoot, 300. 
Sparrow, English, dissection of, 

(facing), ^327 ; life-history and 

habits of, 335; structure of, 327; 

western chipping, ^360. 
Sparrow-hawk, 353. 
Spatula clypeata, 347. 
Species, defined, 69, 
Species-extinguishing, 442. 
Species-forming, 408, 442. 
Speotyto cunicularia, 353. 
Sphinx c/iersis larva, ^'431. 
Sphinx-moth, pen-marked, larva, 

*43L 

Sp/iyma, 280. 
Spicules, sponge, 85. 
Spider and web, ^237. 



Spider, crab, -235; jumping. *235 
long-legged, ^233; running, ^234, 
running with egg-sac, ^234; tri- 
angle, and web, *238. 

Spider-crab, 154. 

Spiders, 229; hunting, 233; seden- 
tary, 233; trap-door, 233; wander- 
ing, 2 33; wtb weaving, 233. 

Spinnerets of spider, *233. 

Spizella socialis arizoncc, "^360. 

Sponge, commercial, 86 ; fresh- 
water, 84; glass, *8j; skeleton of, 
88; structure of, 88. 

Sponges, 84; calcareous ocean, 8^; 
classification of, 91; development 
and life-history of, 89 ; feeding 
habits of, 88 ; form and size of, 
87; of commerce, 90. 

Spongin, 86. 

Spougilla sp., 84. 

Springtail, American, *i8i. 

Squamata, 312. 316. 

Squid, great, ^25 7. 

Squids, 255, 257. 

Squirrels, 391. 

starfish, ^109; cross-section of, *I12. 

Starfishes, 108, 121. 

Stent or sp., *79. 



Ster 



145- 



Sterna maxima, 194. 
Sting-rav, 281. 
Stone-fly, *i82. 
Strix pratincola, 353. 
Strongylocentrolus sp., structure of, 

"3- 

Strongylocentrotus fr ant is can us, 

*H5, 122; structure of, 115. 

Struggle for existence, 406. 

Strut hi o armelus, 342. 

wSub-species, 69. 

Suckers, 283. 

Sucking-bugs, 197. 

Sun animalcule, *78. 

Sunfish, dwarf, 271 ; golden, dissec- 
tion of, (facing) *263; life of, 270; 
structure of, 263. 

Supplies, obtaining laboratory, 453. 

Swans, 347. 

Swarming of honey-bee, 219. 

Swell-fish, 285. 

Swift, common, 316. 

Sword-fish, 285. 

Symbiosis, 155, 413. 

Symmetry, bilateral, 5; radial, 108, 

Sympetrum Mo turn, ^196, 



INDEX 



483 



Syngnathus fuscnm. 285. 

Tadpole, 55. 

Tadpoles, ^296. 

Teenia solium, 139. 

Tapeworm, 139. 

Teal, blue winged, 347 ; green- 
winged, 347. 

Teleostomi, 282. 

Tell-tale, 349. 

Teredo, 251. 

Tern, 194, 

Terns, 345. 

Terrapin, diamond-back, 314; red- 
bellied, 314; yellow-bellied, 314. 

Test i ido sp., "^315. 

Tetragnatha sp., ^233. 

Thalarctos maritimus. 398. 

Thamnophis sp.. life of, 307; struc- 
ture of, 303. 

Thamnophis pari eta lis, ""320. 

Theridise, 235. 

Therioplectes sp., cornea of com- 
pound eye of, *i86. 

Thomisidse, 235. 

Thrasher, sickle-billed, *37i. 

Thrush, russet backed, ^363. 

Thy ma //its signifer, 284. 

Ticks, 229. 

Tiger-beetles, 209. 

Toad, cellular structure of, 40; de- 
velopment of, 55; garden, dissec- 
tion of, 5; horned, 317 ; skeleton 



of, 



11 



Toads, 299, 300. 

Torpedo, 281. 

Tortoise, Galapagos giant, *3i5- 

Tortoises, 313. 

Tortoise-shell, 315. 

Tot anus melanoleucus, 349. 

Trachea, *i84. 

Tree-frogs, 300. 

Tree-toads, 300. 

Trepang, 124. 

Trichina, 140. 

Trichina spiralis, 141, *I4I. 

Trichinosis, 141. 

Triopha modes ta, ^254. 

Tripoli rock, 82. 

Triton, green. 297. 

Trochi/us colitfiris, 356 ; nest and 

eggs of, *357. 
Trout, rainbow, ^283. 
Tumble bugs, 209. 
Tnrdus ustnlains, ^363. 



Turkeys, wild. 350. 

Turtle, green, 315 ; hawk-bill, 315 ; 

logger-head, 315. 
Turtle-dove, 351. 
Turtles, 313. 

Tympamtchns americanus, 350. 
Tyroglyphus siro. ^230. 

Ungulata, 393. 

Unto sp., life-history and habits of, 

243; structure of, 239. 
Uria troile calif or nica, ^344. 
Ursus americanus, 398. 
Ursus horribilis, 398. 

Varanus nilotict/s, 318. 

Variation, 406. 

Variety, 69. 

Ve nation of wings of insects, 174; of 
wings of Monarch butterfly, *I75- 

Venus mercenaria, 247. 

Vermes, 127; life-history and hab- 
its of, 132; classification of, 135. 

Vertebrate, denned, 30; brains of, 
376; eye of, ^379. 

Vertebrates, 259; structure of, 259. 

Vespidae, 217. 

Vinegar-eel, 140, ^140. 

Viper, 324; blowing, 321. 

Viper a cerasta, 324. 

VorticeUa sp., ^76. 

Vorticella, structure and life of, 75. 

Vulpes pennsylv aniens, 398. 

Walking-stick, 193, 194. 
Wapiti, *394. 

Wasps, 2 12; digger, 217; solitary, 2 17. 
Water-beetle, predaceous, 210. 
Water-beetles, 206. 
Water-boatman, ^199. 
Water-boatmen, 197. 
Water-flea, 148, ^149. 
Water-dog, 298. 
Water-snake, 320. 
Water-strider, 197, 199, *I99. 
Water tiger, 212, ^214. 
Weevils, 209. 
Whalebone, 393. 
Whales, 393. 
Wheel-animalcule, *H3. 
Whip-poor-will, 356. 
Whitefish, 284. 
Wild-cat, 398. 

Wings of Monarch butterfly showing 
venation, *I75- 



4 8 4 



INDEX 



Wolf, 398. 

Woodchuck, 391. 

Wood-duck, 347. 

Wood- frog, 300. 

W^ood-lice, 150. 

Woodpecker, California, 356; ivory- 
billed, 355; red-headed, 355. 

Woodpeckers, 354. 

Wood-rat, 391. 

Worm, army, *2II. 

Worms, 127; life-history and habits 
of, 133; classification of, 135; ma- 
rine, *I34. 



Xiphias gladius % 285. 

Yellow-hammer, ^355. 
Yellow-jackets, 217. 
Yellow- shank, 349. 

Zenaidura macroura, 351. 

Zoogeography, 436. 

Zooids, 98. 

Zoology, a first course in, 3; de 
fined, 3; divisions of, 2; system- 
atic, defined, 3. 

Zoophytes, 92. 



SCIENCE TEXT-BOOKS 
AND WORKS OF REFERENCE 



All prices are net unless marked retail. Details of the books will be 
found in Henry Holt cV Co/s Educational Catalogue or in their Miscel- 
laneous List, which will be sent free on application. 

American Science Series 

Physics. By Prof. George F. Barker of the University of Pennsylvania. 

Advanced Course, 902 pp. 8vo. $3.50 

Chemistry. By Prof. Ira Remsen of Johns Hopkins. 

Advanced Course. 850 pp. 8vo. $2.80 

The same. Briefer Course. {New Edition, 1901.) ,435 pp. 121110. $1.12 

The same. Elementary Course. 272 pp. 12010. 80c. 

Laboratory Manual^ Elementary Course). 196 pp. i2mo. 40c. 
Chemical Experiments. By Prof. Remsen and Dr. W. W. Randall. {For 

Briefer Course.) No blank pages for notes. 158 pp. 121110. 50c. 

Astronomy. By Prof. Simon Newcomb of Johns Hopkins and Edward S. 

Holden, late Director of the Lick Observatory, California. 

Advanced Course. 512 pp. 8vo. $2.00 

The same. Briefer Course. 352 pp. 121110, $1.12 

The same. Elementary Course. By E. S. Holden. 446 pp. izmo. $1.20 

Geology. By Profs. Thomas C. Chamberlain and Rollin D. Salisbury 
of the University of Chicago. {In preparation.) 

General Biology. By Prof. W. T. Sedgwick of Massachusetts Institute of 
Technology and Prof. E. B. Wilson of Columbia College. {Revised and 
Enlarged, 1896.) 231 pp. 8vo. $i-75 

Botany. By Prof. C. E. Bessey of the University of Nebraska. 

Advanced Course. 611 pp. 8vo. $2.20 

The same. Briefer Course. 356 pp. $1.11 

Zoology. By Prof. A. S. Packard, Jr., of Brown University. 

Advanced Course. 722 pp. 8vo. $2.40 

The same. Briefer Course. 338 pp. $1.12 

The same. Elementary Course. 290 pp. i2mo. 80c. 

The Human Body. By H. Newell Martin, sometime Professor in the 

Johns Hopkins University. 
Advanced Course. 685 pp. 8vo. $2.50 net. Copies without chapter on 

Reproduction sent when specially ordered. 
The same. Briefer Course. {Entirely new edition revised by Prof. G. 

Wells Fitz of Harvard^) 408 pp. i2mo. $1.20 

The same. Elementary Course. 261 pp. i2mo. 75c. 

The Human Body and the Effects of Narcotics. 261 pp. i2mo. $1.20 

Psychology. By Prof. William James of Harvard. 

Advaticed Course. 689 + 704 pp. 8vo. 2 vols. $4.80 

The same. Briefer Course. 478 pp. i2mo. $1.60 

Ethics. By Profs. John Dewey and James H. Tufts of Chicago University. 
{In preparation.) 

Political Economy. By the late President Francis A. Walker of Massa- 
chusetts Institute of Technology. 

Advanced Course. 537 pp. 8vo. &2.00 

The same. Briefer Course. 415 pp. i2mo. t si. 20 

The same. Elementary Course. 423 pp. i2mo. $1.00 

Finance. By Prof. Henry Carter Adams of the University of Michigan. 
Advanced Course, xiii + 573 pp. 8vo. $3-5° 

vii *oi 2 



Henry Holt $r Co.'s Works on Science 

Allen's Laboratory Exercises in Elementary Physics. By Chas. R. 

Allen of the New Bedford, Mass., High School, x -f- 209 pp. Pupils" 
Edition, 80c. Teachers* Edition, $1.00 

Arthur, Barnes, and Coulter's Handbook of Plant Dissection. By Prof. 
J. C Arthur of Purdue University, Prof. C. R. Barnes of University 
of Chicago, and Pres. John M. Coulter of Chicago University, xi -\- 256 

pp. $1.20 

Atkinson's Elementary Botany. By Prof. Geo. F. Atkinson of Cornell. 
Fully Illustrated, xxiii + 441 pp. $1.25 

Lessons in Botany, illustrated. 365 pp. $1.12 

Barnes's Plant Life. By Prof. C. R. Barnes of University of Chicago. 
Illustrated, x -j- 428 pp. $1.12 

Outlines of Plant Life, illustrated. 308 pp. $1.00 

Beal'S Grasses of Worth America. For Farmers and Students. By Prof. 
W. J. Heal of Michigan Agricultural College. Copiously illustrated. 
8vo. Vol. I, 457 pp., $2.50. Vol. II, 707 pp., $5.00 

Brit ton *s Manual of the Flora of the Northern States and Canada. By 

Prof. N. L. Britton, Director of N. Y. Botanical Gardens. {In press.) 

Bumpus's Laboratory Course in Invertebrate Zoology. By Prof. H. C. 

Bumpus of Brown University. Revised. 157 pp. $1.00 

Cairns' Quantitative Chemical Analysis. By Fred'k A. Cairns. Revised 

and edited by Dr. E. Waller. 417 pp. 8vo. $2.00 

Congdon's Qualitative Analysis. By Prof. Ernest A. Congdon of Drexel 
Institute. 64 pp. Interleaved. 8vo. 60C. 

Crozier's Dictionary of Botanical Terms. 202 pp. 8vo. $2.40 

Ganong's Laboratory Course in Plant Physiology. By William F. 
Ganong, Professor of Botany in Smith College, vi -f- 147 pp. 8vo. 

$1.00 

Hackel's The True Grasses. Translated by F. Lamson-Scribner and 
Effie A. Southworth from k4 Die natlirlichen Pflanzenfamilien." 

v-(--228pp. 8vo. $1.50 

Hall's First Lessons in Experimental Physics. By Prof. Edwin H. Hall 

of Harvard, viii + 120 pp. i2mo. 65c. 

Hall's and Bergen's Text -book of Physics. By Prof. Edwin H. Hall 

and Joseph Y. Bergen, Jr., Junior Master in the English High School, 
Boston. Greatly enlarged edition. 596 pp. i2mo. $1.25 

Hertwig's General Principles of Zoology. From the Third Edition of Dr. 

Richard Hertwig's Lehrbuch der Zoologie. Translated and edited by 
Prof. George Wilton Field. 226 pp. 8vo. $1.60 

Howell's Dissection of the Dog. As a Basis for the Study of Physiology. 
By Prof. W. H. Howell of Johns Hopkins, 100 pp. 8vo. $1.00 

Jackman's Nature Study for the Common Schools. (Arranged by the 
Months). By Wilbur Jackman of the Cook County Normal School, Chi- 
cago, 111. 448 pp. $1.20 

KellOgg's Elements of Zoology. By Prof. Vernon L. Kellogg of Leland 
Stanford University. (J n preparation.) 



Henry Holt Sr Co/s Works on Science 

Kerner and Oliver's Natural History of Plants. Translated by Prof. F. 

W. Oliver of University College, London. 4to. 4 parts. With over 
xooo illustrations and 16 colored plates. $15.00 

Kingsley's Vertebrate Zoology. By Prof. J. S. Kingsley of Tufts Col- 
lege. Illustrated. 439 pp. 8vo. $3.00 

Elements of Comparative Zoology. 357 pp. i2mo. $1.20 

Macalister's Zoology of the Invertebrate and Vertebrate Animals. By 

Alex. Macalister. Revised by A. S. Packard. 277 pp. i6mo. 8cc. 

Macloskie's Elementary Botany. With Students' Guide to the Examina- 
tion and Description of Plants. By George Macloskie, D.Sc, LL.D. 
373 PP. $i-3o 

MacMillan's Plant Embryology. By Prof. Conway MacMillan of the 
University of Minnesota. (/» preparation.) 

McMurrich's Text-book of Invertebrate Morphology. By Prof. J. Play- 
fair McMurrich, M.A., Ph.D., of the University of Cincinnati, vi 4- 661 
pp. 8vo. New Edition. $3.00 

McNaVs Botany. Outlines of Morphology, Physiology, and Classification of 
Plants. By William Ramsay McNab. Revised by Prof. C. E. Bessey. 
400 pp. i6mo. 80c. 

Merriam's Mammals of the Adirondack Region. With an Introduction 

Treating of the Location and Boundaries of the Region, its Geological 
History, etc. By Dr. C. Hart Merriam. 316 pp. 8vo. I3.50 

Nicholson and Avery's Exercises in Chemistry. By Prof. H. H. Nichol- 
son, University of Nebraska, and Prof. Samuel Avery, University of 
Idaho. 134 pp. 60c. 

Noel's Bnz ; or, the Life and Adventures of a Honey Bee. By Maurice 
Noel. 134 pp. Retail, $1.00 

Hoyes's Elements of Qnalitative Analysis. By Prof. Wm. A. Noyes of the 

Rose Polytechnic Institute. 91 pp. 8vo. 80c 

Packard's Entomology for Beginners. For the use of Young Folks, 

Fruit-Growers, Farmers, and Gardeners. By A. S. Packard, xvi-f-367 
pp. Third Edition, Revised. $1.40. 

Guide to the Study of Insects, and a Treatise on those Injurious and 

Beneficial to Crops. For Colleges, Farm-Schools, and Agriculturists. 
By A. S. Packard. With 15 plates and 670 wood-cuts. Ninth Edition. 
715 pp. 8vo. $5.00 

Outlines of Comparative Embryology. Illustrated. 243 pp. 8vo. $2 50 

Peabody's Laboratory Exercises in Anatomy and Physiology. By Jas. 

Edward Peabody of the Peter Cooper High School, New Vork. x + 
79 pp. Interleaved. 121110. 60c. 

PercivaPs Agricultural Botany. By Prof. John Percival of the South- 
eastern Agricultural College, Wye, England, xii + 798 pp. 121110. $2.50 

Perkins' Outlines of Electricity and Magnetism. By Prof. Chas. a. 
Perkins of the University of Tennessee. 277 pp. iamo. $1.10 



Henry Holt & Co.'s Works on Science 

Pierce's Problems of Elementary Physics. Chiefly numerical. By E. 
Dana Pierce of the Hotchkiss School. 194 pp. 60c. 

Randolph's Laboratory Directions in General Biology. By Miss Harriet 

Randolph, Instructor in Bryn Mawr College. 163 pp. 80c. 

Reighard and Jennings's Anatomy of the Cat. By Profs. Jacob Reighard 
and H. S.J knnings of the University of Michigan. xx-j-498 pp. 8vo. $4.00 

Schenck and Gtfrber's Outline of Human Physiology. Translated by Dr. 
William D. Zoethout. With prelace by Prof. Jacques Loeb of the Uni- 
versity of Chicago, viii -f- 339 pp. 8vo. $i«75 

Scudder's Butterflies. By S. H. Scudder. 322 pp. umo. $1.50 
Brief Guide to the Commoner Butterflies, xi -f 206 pp. Retail^ $1.25 

The same . With 21 plates, containing 97 illustrations. Retail, $1.50 

The Life of a Butterfly. A Chapter in Natural History for the General 

Reader. 186 pp. i6mo. Retail, $1.00 

Torrey's Elementary Studies in Chemistry. By Joseph Torrby, Jr., In- 
structor in Harvard. 487 pp. i2ino. $1.25 

Underwood's Our Native Ferns and their Allies. By Prof. Lucien M. 
Underwood of Columbia. 156 pp. $1.00 

— Moulds, Mildews, and Mushrooms. Illustrated. 236 pp. $1.50 
Wheeler's The Elements of Animal Embryology. By Prof. William 

No'nTON Wheeler of the University of Texas. {In preparation?) 

White's Qualitative Analysis. By Prof. John White of the University of 

Nebraska. 820 pp. 80c. 

Williams's Elements of Crystallography. By George Huntington Will- 
iams, late Protessor in the Johns Hopkins University, x -{- 270 pp. Re 
vised and Enlarged, $i'25 

Williams's Geological Biology. An Introduction to the Geological History 
of Organisms. By Prof. Henry S. Williams of Yale. 8vo. 395 pp. $2.80. 

Woodhull's First Course in Science. By Prof. John F. Woodhull of the 
Teachers' College, New York City. 
/. Book of Experiments, xiv -{- 79 pp. 8vo. Paper. 50c. 

//. Text-book, xv + 133 pp. i2mo. Cloth. 65c. 

Woodhull and Van Arsdale's Chemical Experiments. An elementary 
manual largely devoted to the chemistry of every-day life. Interleaved. 
136 pp. 60c. 

Zimmermann's Botanical Microtechnique. Translated by James Ellis 
Humphrey, S.C. xii + 296 pp. 8vo. $2.5° 



HENRY HOLT & CO., 378 WabLh AVe.*Chicago 



TWO BOOKS BY THE LATE 

FRANCIS A. WALKER 

President oj the Massachusetts Institute of TccJinology 



DISCUSSIONS IN ECONOMICS AND STATISTICS 

Edited by Professor Davis R. Dewey. 

With portrait. 454 + 481 pp. 2 vols. 8vo. $6.00 net. 

Important papers on Finance, Taxation, Money, Bimetallism, Economic 
Theory, Statistics, National Growth, Social Economics, etc. Ihe author had 
hoped to bring- these papers together himself. 

The Dial: ''Professor Dewey has performed a real service to the 
public, as well as to the memory of his late chief. ... In the present 
collection the editor has not included everything General Walker ever 
wrote, but has aimed, so far as possible, to avoid repetitions of 
thought .... there are some discussions of the national finances in 
the period following the Civil War, which have a timely as well as his- 
torical interest at the present time. . . . To improve the census was 
General Walker's work for many years, and his experience cannot fail 
to be of interest to the present generation. . . . Economics in the hands 
of this master was no dismal science, because of his broad sympathies, 
his healthy, conservative optimism, his belief in the efficacy of effort ; 
and, in a more superficial sense, because of his saving sense of humor 
and his happy way of putting things .... he was the fortunate pos- 
sessor of a very pleasing literary style .... clear and interesting to 
the general reader, as well as instructive to the careful student. There 
could have been no more fitting monument to his memory than these 
two volumes, together with the other volume of ' Discussions in Educa- 
tion.'" 

New York Commercial Advertiser : "Clear, direct and forceful, full of 
familiar illustration and appeal to fact, and always interesting. Cer- 
tainly no other man has had such a wide influence on the economic 
thought of America, or has done so much to elevate it. . . . This state- 
ment, however, can give no adequate notion of the wealth of material 
or wide scope of subjects covered by these shorter articles .... one 
can almost hear the spoken word in some of the adresses .... an 
excellent index." 

DISCUSSIONS IN EDUCATION 

Edited by James Phinney Munroe. 342 pp. 8vo. $3.00 net. 

The author had hoped to collect these papers in a volume himself. 

The Dial : "A fitting memorial to its author. . . . The breadth of his 
experience, as well as the natural range of his mind, are here reflected. 
The subjects dealt with afe all live and practical. . . . He never deals 
with them in a narrow or so-called ' practical ' way." 

Literature : "The distinguishing traits of these papers are open- 
mindedness, breadth, and sanity. . . . No capable student of educa- 
tion will overlook General Walker's book ; no serious collection of 
books on education will be without it. The distinguished author's 
honesty, sagacity, and courage shine on every page." 

The Boston Transcript : " Two of his conspicuous merits characterize 
these papers, the peculiar power he possessed of enlisting and retaining 
the attention for what are commonly supposed to be dry and difficult 
subjects, and the capacity he had for controversy, sharp' and incisive, 
but so candid and generous that it left no festering wound." 

UCXIDV \AC\\ T %t CC^l 29 West 23d St., New York 
nClNtVI nULl CX K^KJ, 378 Wabash Ave., Chicago 

ii 1900 



CHEMISTRY 



CAIRNS'S QUANTITATIVE CHEMICAL ANALYSIS 

By Frkd&kick A. Cairns Entirely 7ieiv edition^ revised and 
enlarged by Dr. E. Wallew. xii-f-417 Pp. 8vo. $2.00, net. 

CQNGDON'S QUALITATIVE ANALYSIS 

By Prof. Ernest A. Congdox, of Drcxel Institute. 64 pp. Inter- 
leaved. 8vo. 60c, net. 

NICHOLSON AND AVER Y' S EXERCISES IN 

CHEMISTRY With Outlines for the StuJy of Chemistry. To 
_■__»_■»_ accompany any elementary text. By Prof. H. H. 
Nicholson, of the University of Nebraska, and Prof. Samuel 
Avery, of the University of Idaho. 413 pp. i2md. 60c, net 

NOYES'S ELEMENTS OF QUALITATIVE 

ANALYSIS By Prof * Wm ' A - Novjes. of the Rose Polytechnic Insti- 

«^^^_____ tute. x + gipp. 8vo. 80c, net. 

REMSEN'S CHEMISTRIES By Prof. IbaRsmsen, of Johns 

-_^ ,« , __ , Hopkins. {American Science 

Series.) 

Inorganic Chemistry {Advanced), xxii 4-853 pp. 8vo. $2.80, net. 

Introdnction to Chemistry {Briefer), xix + 435 pp. izmo. $1.12, net. 

In addition to its pronounced success in this country, where it is 
used in hundreds of schools and colleges, the book has passed through 
several editions in England, and has been translated into German 
(being the elementary text-book in the University of Leipsic) French, 
and Italian. 

Remsen and Randall's Experiments {for the "Introduction"). 

50c, vet. 
Elements Of Chemistry {Elementary), x -f- 272 pp. i2mo_ 80c, net. 
Laboratory Manual {for the " Elements"). 40c, net. 

TORRE Y'S ELEMENTARY CHEMISTRY 

By Joseph Torrey, Jr., of Harvard. 437 pp. i2mo. $1.25, net. 

The Dial : " It combines lectures and demonstrations with labora- 
tory work in a manner that commends itself strongly to our appro- 
val. ... It was time for some one to say these things, and we com- 
mend, the book most heartily. The essential aim of the author is to 
restore the disciplinary value of the study, and his method is well 
worthy of attention." 

WOODHULL AND VAN ARSDALE'S CHEMICAL 
EXPERIMENTS *J Prof - J°» N F . x Wo ? DH V' r L ,r id M m r v Va ? 

,.___ Arsdale, both 01 Teachers College, New York 

City. 136 pp. i2mo. 60c, net. 
Extremely simple experiments in the chemistry of daily life. 

MCXiny MA| T 0. f^r\ 29 West 23d St , NEW YORK 
tiClNKl nULI CX^U, 378 Wapash Ave., CHICAGO 

vi, 1900 



RUSSIA 

KRAUSSE'S RUSSIA IN ASIA, 1558-1899 

With appendix, index, and twelve maps. 8vo. $4.00. 

Boston Transcript : " The most masterly marshaling of the 
British arguments against Russia which has appeared in a long 
time. . . . The man who wrote the book has had an inside 
view of Russian methods, or else he is extremelv clever in col- 
lecting detailed information about them. His information is 
brought down to date, and his passages on the Manchurian 
railway agreement show that he can see near things as vividly 
as far things. His review of the present state of Russia's 
southern boundary in Asia is striking, and sums up a great 
deal of history." 

THOMPSON'S RUSSIAN POLITICS 

By Herbert M. Thompson. An account of the relations of 
Russian geography, history, and politics, and of the bearings 
of the last on questions of world-wide interest. With maps. 
i2mo. $2.00. 

Outlook: "The result of careful study, compactly, clearly, 
and effectively presented. . . . The author's aim is to stir the 
friends of freedom throughout the world to a deeper interest in 
the cause of Russian liberty. His work is vivified by the fact 
that his heart is in it." 

WALLACE'S RUSSIA 

By D. Mackenzie Wallace, M. A., Member of the Imperial 
Russian Geographical Society. Large i2mo. $2.00. 

Contents include: In the Northern Forests; Voluntary 
Exile ; The Village Priest ; A Peasant Family of the Old Type; 
The Mir, or Village Community ; Towns and Mercantile 
Classes; Lord Novgorod the Great; The Imperial Adminis- 
tration ; The New Local Self-Government ; Proprietors of 
the Modern School ; The Noblesse ; Social Classes ; Among 
the Heretics ; Pastoral Tribes of the Steppes : St. Petersburg 
and European Influence ; Church and State ; The Crimean 
War and Its Consequences ; The Serfs ; The New Law 
Courts ; Territorial Expansion and the Eastern Question. 
Nation: " Worthy of the highest praise. . . . Not a piece of 
clever book-making, but the result of a large amount of serious 
study and thorough research. . . . We commend his book as 
a very valuable account of a very interesting people." 

GAUTIER'S A WINTER IN RUSSIA 

By Theophile Gautier. Translated by M. M. Ripley. 
i2mo. $1.75. 

Contents : Berlin ; Hamburg ; Schleswig ; Liibeck ; Cross- 
ing the Baltic ; St. Petersburg ; Winter ; The Neva ; Details 
of Interiors ; A Ball at the Winter Palace ; The Theatres ; 
The Tchoukine Dvor ; Zichy ; St. Isaac's ; Moscow ; The 
Kremlin ; Troiftza ; Byzantine Art ; Return to France. 
New York Tribune: "As little like an ordinary book of 
travel as a slender antique vase filled with the perfumed wine 
of Horatian banquets is like the fat comfortable tea-cup of a 
modern breakfast-table." 

HENRY HOLT & CO. 29 ^SW^tri*™ 01 

vii, 1900 , 



Champlin's Young Folks' Cyclopaedia of 

LITERATURE AND ART 

"With 270 illustrations. 604 pp. &vo. $2,50 

Brief accounts of the great books, buildings, statues, pictures, operas, 
symphonies, etc. 

11 Few poems, plays, novels, pictures, statues, or fictitious characters 
that children — or most of their parents — of our day are likely to in- 
quire about will be missed here. . . . Mr. Cbamplin's judgment 
seems unusually sound — will be welcome and useful." — Nation. 

" Every schoolboy should have it on his study table. . . . The 
range of the volume is very wide, for besides those items of classical 
knowledge which constitute the average school encyclopaedia, we 
have brief descriptions given of modern books, poems, inventions, 
pictures, and persons about which the lad of the period should be 
acquainted. . . . The pictures in the volume are varied and truly illus- 
trative. Old pictures and sculpture are presented in the usual line 
of drawings, but modern scenes and buildings are pictured through 
excellent half-tone reproductions of photographs," — N. Y. Ti?>ies Sat- 
urday Review, 

" He has covered the ground with great completeness; and, though 
his notices are necessarily brief, they give the salient facts that bring 
understanding. ... It may be, too, that its completeness will make 
it serviceable as a reference book to many of maturer years." — 
JV, Y. Tribune. 

"The four books together would constitute the best sort of a gift 
for a young person of inquiring mind." — The Dial. 

u A most valuable reference book for schoolboys and -girls."- — 
Bookman. 

"A good book to buy for the young folks and use yourself. It 
contains a great deal of handy information which, unlike the young 
folks, most of us have had time to forget." — Life. 

"A commendable feature is the clear way in which synopses of all 
the principal operas are given." — Providejice [ournal. 

Earlier Volumes of Champlin's Young Folks' Cyclopaedia* 
With numerous illustrations. 8vo. $2*50 each* 

COMMON THINGS. PERSONS and PLACES. 

GAMES and SPORTS. 

#*£ 12-page circular, with sample pages of Champlin's Young 
Folks' Cyclopcedias and his other books, free. 

HENRY HOLT & CO. fWffi^g£5E& 

iv '02 . ^^^ 

0& 













\^ 



^# ; 











v. . « x 















m 






S; 



*+ 












R , 









~*± V* 









u r 





















'U 






' 



x°^. 









<p 












* 






v 









*\ 









A - 

^ A it* * -/> 



n\^ V 












Oo 






















" o*' 









% 















^ '' 



* * * s 



cfr* 



v\ 






Oo 












* 















.A 






/--* 






■<b O 






>- *<» 









<" <\ 










